what has changed are the conditions around sexuality in our society which have been driving more people towards fetishes; more hardcore pornography is a part of that, but if you really wanna get to the root of things it's probably based upon the artificial difficulty of having normal heterosexual relations that has been imposed by various factors societally (most recent being feminism). therefore niggas withdraw and wank, losing any connection to real sex because there aren't any women around em, and bitches get ruined by smut
the childhood exposure part is important but in order for a fetish to be really imprinted it needs specific circumstances to grow