JLo started the trend with fat butts. But there was a time before her when gamers unironically called Mai's ass flabby. I remember a British forum called Higher Voltage (since long defunct) where they had a "tournament" where users could vote for the best ass in fighting games. They excluded Mai from the get go with the quote "I excluded Mai because hers is a little flabby". And no one, at that time, had any problems with that.
People are getting fatter and fatter, and I think, sadly, that it's only natural, as a result, that people today think overweight is normal, and that obesity is just overweight. If most people around you are overweight, that is normal from a certain perspective. And this is also how degeneration takes over a society. It often starts with people having it too easy and not having to struggle. They get fat, lazy and ignorant as a result.
I don't question people who likes Mai's ass. But I do question people who call it firm, when it wobbles like a lump of jello from a mere kick.