You Are Old, Father William, Wiki article, includes complete poem.
I have a cousin like that. I think my brother and myself are among the few people who will ever socialize with him (and I do it largely out of pity, but not very often). It’s painfully obvious that he’s even more socially crippled than I am and has been all his life (he’s about 15 years older than me). He’s been terribly lonely pretty much all his life. In his case, it’s plainly obvious that his non-stop questioning is his monumental but messed-up attempt to appear interested in the other person and to make conversation. I’ve told him a few times that it feels like he’s interrogating me. I think he’s tried to keep it down somewhat in recent years.
He does the same with wait-persons at restaurants, asking 500 questions about the details of the menu, asking about the ingredients, asking for all kinds of special substitutions or special ways he’d like the chefs to prepare his food, ad infinitum. The people with him find this seriously embarrassing, to the extent that nobody wants to dine with him in restaurants any more (even including his own sister). My brother and I have decided we’ll only eat with him at buffet-style restaurants, which has proved to be a successful strategy in that regard.
ETA: For many years, he’s tried to cope with his cosmic lonliness by taking up Buddhism. Sometimes, when he asks me too many questions, I just answer “Mu”.
That may be it. I had thought that such people were just accustomed to “power,” due to authority or status, but this behavior happens too with people who aren’t in power of any sort, and maybe Aspie or something like that is what’s up.
I work with a few folks who will stop by because they need something from me but they have difficulty getting to asking me for it. They usual opener is a “how are things going” or “what’s up”.
Do not answer this question.
Just respond, depending on how you’re feeling:
What can I do for you?
Do you need something from me?
What do you want?
The chain of "why"s is what tipped me off. It implies the questioner can’t, or won’t understand the rationale for your answer. Said another way, that person can’t or won’t get in sync with you. Classic Asbergerish behavior as I understand it. Not that I claim any expertise besides having dealt with a few.
Why do you want to stop train of questions people?
I’ve never encountered this. Either I hang around generally sane people, or they realize that if they dig beneath my neutral “fine” they’ll eventually break through the retaining wall into a flood of petulant complaining about life that nobody -and I mean nobody- wants to hear.
There could be several reasons to do a train of questions.
Sometimes the other person responds with meaningless dribble like repeating what you just said in slightly different words, or “That’s cool”, “Nice” etc, because they are not motivated/interested. And you feel bored but are stuck with that person for some reason, so you see if you can extract anything interesting for entertainment. Though I would not use boring questions like the ones presented in the first post, those leave an impression of desperation.
I have known some people who were very unemotional and did not have opinions on things, so they didn’t really have anything to say but ask questions (there are men and women like that).
It could be due to autism spectrum, where you have an analytical side that is very dominant.
Sometimes when I am taught something analytical I have many questions which I need to have answered to make the connections between the new idea and everything else that I know. These, to the other person appear often meaningless or totally unrelated. If I wait to get the answer without asking the question (which I try to), I often forget it, and later feel I have gaps in my understanding. Often times when you are learning something you can also ask too many questions, because you are not done making all the connections, so part of the questions are redundant.
I tend to be blunt. My time is too valuable to waste in idiocy.
I’d ask them “Do you actually have something to tell me? If so, say it. If not, I’m leaving.”
And I do exactly that.
How does wanting to stop train of questions people make you feel?
From the internets:
10 CONVERSATION KILLERS
For when you need to shut things down…
When eating a mini roast beef canapé, say, “If you chew slowly enough you can hear the cow’s soul“
“Sorry, I just have to take this call outside – it’s Downing Street.”
Start crying with no explanation.
“I have a sex tape – want to see it?” (get your phone out)
“What’s your favourite emoji? Let’s go through them and score each one out of ten.”
“Who wants to get really drunk? First one to barf wins a mystery prize.”
“Shut your eyes and count to ten and I’ll go and hide.” Then leave.
Push someone down the stairs.
“I’ve given up sugar and here’s why I think you should too.”
“Did you know artificial strawberry flavouring is made from the anal glands of a beaver?”
In the late 1980s, I discovered that telling people I had recently become a vegetarian made them stop talking to me.
Also, I have a friend who drives a cab. She has a long list of things she does not like to hear about. Top ten include the accident, break-down, or DUI that led you to taking a cab today, and the reason you are on your way to the doctor.
I could ask her for the complete list, if you want.
LOL! This is what I do too ! I will say I am busy and walk away or say "I can’t hear you "then walk away.
“Haven’t had to kill anyone yet today.”
If that doesn’t shut a person down, an ice cold, “Day’s not over yet,” does the trick.
Now if you want to shut them down without them thinking you are a psychopathic asshole, you might want to take someone else’s advice, but this works for me.
Or your average 3- to 6-year-old.
Agree about the 4yo. “Why” is their second favorite word after “no”. 
The OP was saying it was somebody culturally respected.
Speaking of whom, I wonder if the OP will come back to fill us in. Lots of folks, including me, have said in effect: “Be a jerk to the jerk.” If this is really something more like his Taiwanese grandfather-in-law who must be venerated by visitors in front of his family I’d like to know more. Especially about what sort of verbal jiu-jitsu he was hoping to learn.
I can think of cultural norms that make it hard to “be a jerk to the jerk” right here in the US of A. My father in law is a serial questioner and I agree it’s passive aggressive. But, he’s my wife’s father and I need to get along with him. I think that he asks these questions looking for a button to push. He will ask my wife about her work until he gets her to reveal something that’s not going well, or that she is worried about and then keep asking her questions until she’s stressed out.
The one trick I will use when I’ve really had enough is to spout off some of my extreme, but sincerely held convictions. He’s one of these ‘middle of the road’ guys in his seventies who is uncomfortable when someone says something explicitly negative or politically extreme. So when he probes too much, rather than keep giving him innocuous answers, I give him deeply held and passionate responses that kind of freak him out and shut it down.
Sorry for being AWOL. I guess, not so much “cultural” (although there’s that) as it just is that someone is in a position of authority or power. Although today if that were to happen again I’d firmly find a way to end the conversation, yes.
I have an old friend I text with regularly who starts every conversation almost exactly like the example in the OP. No matter what my answer is to “How are you?” - whether it’s good, meh, fine, okay, not bad, not great, etc - the next answer will always be “Why?”
I try to appreciate that he is trying to make small talk somewhat more meaningful, and of course if my answer is something that implies I am exceptionally good or bad I can understand wanting to know more, but I do wish I could figure out how avoid that tedious “why?” when I am just fine and really have nothing further to say about it.
It’s your conversation too: you’re not obligated to respond to his questions. You can change the subject any time you want. You can do this directly, or indirectly.
A: How are you?
B: Fine, how are you?
A:What does “fine” mean?
B: I’m cooking pasta tonight. I 've got a new recipe using plums that I want to try. Do you like plums?
A: Are you doing OK?
B: I’ve got a load of plums cheap at the supermarket. What are you eating?
A: I mean, is everything ok with your family?
B: The thing about plums is that they are all imported (at this point, move off into your favorite rant about Trump, the GOP, and the manipulation of the plum market)
– or whatever floats your boat