I'm pretty sure this falls into the sissy fetish more than the adult baby world. Sissy fetishes center on the subject making himself pathetic, vulnerable, girlish, humiliated, disgusting, and mocked, often by an attractive dominating woman. The fact that we're laughing at this guy or mocking him probably helps to get him off.
There were some pretty horrible ones on POE Red years back. One had a very beautiful dominatrix tell the sissy (who somehow had the time and money to convert an entire house into a sissy kingdom) to make a menu that he had to stick with the entire week, and all the recipes had his own pee in them. He then had to eat the meals while dressed like this guy while the dom laughed at him and watched, mostly in disgust.
He self-identifies as an adult baby. Check his channel - hundreds of videos just like this one, plus the occasional "adult babies vs the world" rant. The makeup and the hairdos scream Sissy, but if Little Lord Fauntleroy says he's an adult baby, I guess I'll take his word for it.
I was always under the impression that the Sissy community was a specialized subset of the gay/crossdressing community, centered on the subject becoming a dainty, ultra-effeminate, petticoat wearing poof. Humiliation and domineering female figures are frequently part of it, but I assumed that this was simply an extra topping which many Sissies enjoyed, rather than a defining feature.