>>712426785
Oldfags usually fit into 3rd reasoning, it was always about having something spicier than lesbianism without looking at a man or ugly bastard. Futanari in hentai had the appeal of the girl's embarrassment rather than any genderbending fantasy.
I don't know what all led to 2nd, but Discord seems to have had a big impact on Zoomers cultivating HRT\Femboy\Shota.