What is the point of this gibberish spam to my web site?

That depends on what that one form is. If it’s a “contact me” on a blog that ten people in the world are interested in, they probably won’t. If it’s the login for Facebook, then probably.

And it only takes a really dumb, easy bot to defeat a single question. Smarter, more sophisticated bots can defeat whole categories of questions, and something like ChatGPT can probably answer nearly as well as a human can.