Why are Italian-American names so badly mispronounced, even by their owners?

My point is that hit would be much less irritating if he just pronounced it in the ordinary Anglicized way, instead of reaching for an “authentic” pronunciation that is incorrect in every way.

Probably. Although we don’t know why he’s doing what he’s doing. It may very well be that he is trying (and failing) to pronounce it the way a bunch of annoyed Italians told him he should. I mean, maybe not, but I do know that whatever you do, someone will criticise.

Yeah, the “flap r” = “d” is very common. The “d” it is most similar to is in the intervocalic flap in a word like “better.” Most Americans pronounce it as something that sounds like “bedder,” but it’s not exactly the same “d” as in a word like “dental.” For years I did not understand why people rendered Zsa Zsa Gabor’s “very very” as “veddy veddy,” until I realized that type of “r” is quite similar to a “d”, but not so much the regular “d” as much as the type you hear in words like “better” or “bottle” or “petal” (in most American dialects; this doesn’t really work in other forms of English where they clearly pronounce the “t”).

At any rate, the flap-r and flap in “better” are very similar sounds, and even their IPA equivalents are quite similar: /r/ vs /ɾ/. So it makes sense for an American English speaker, at least, to hear it as and reproduce it as a “d” of some sort.

If I try to pronounce that kind of R, it’s possible to notice me preparing my ‘run up’ to saying the word - it sounds awkward because you hear me speaking naturally, then sort of brace myself to pronounce something in a way that is foreign to my tongue

He has said in interviews that he says it that way because it is the authentic Italian pronunciation.

There are Italian dialects where r and d switch, like the way “Madonna!” comes out as “Maronn’!” in some Neapolitan dialects. Where are the Fieris from, and what does their dialect do?

Fair enough, but that still doesn’t really expose what events motivated him to care to try

There’s no mystery when it comes to Guy Fieri. He has talked about it a lot. He changed his name from Guy Ferry to Guy Fieri to honor his Italian heritage (I think “Fieri” might have been his ancestral family name before it was changed to “Ferry”) and he uses the pronunciation he uses because he thinks it is the authentic Italian pronunciation.

Fair enough so

Okay, as a celebrity his genealogy is pretty public. His immigrant great-grandfather was Giuseppe Fieri. It’s a little harder to track down where he’s from, but the one tree I found on Ancestry said he was from Arsago Seprio in Lombardy. If that’s the case, his pronunciation seems off, but I’m a little dubious about the source, as Fieri isn’t really a Lombard name. It seems to be from Tuscany and Lazio.

I’m still inclined to think the explanation given above is correct, that he heard /fiεɾi/ and was used to only hearing /ɾ/ in words like wedding, and maybe was able to contrast it with full-on rolled /r/, so mis-parsed the R sound in “Fieri” as a D sound.