It's because paraphilias come in clusters. Where there is troon, there is also scat, bestiality and kiddy diddling. Based Ray B has been onto them for decades.
But wait, there's more! According to some research, about half of all pedos fantasize about being the gender and age they're attracted to (gay pedos want to be little boys, straight pedos want to be little girls). So pedos are not only commonly troons, they're also age regression fags. There are several possible explanations, but the most obvious are:
a) the pedo in question is mitigating guilt by pretending he's a kid also;
b) autists and other retards possess an explosive mix of entirely uninhibited sexuality and lack of self awareness, which causes them to eventually sexualize their retarded "special interests". First you were a retard obsessed with planes and trains, then puberty hit and now you want to fuck a plane/train anthro abomination from Deviantart. Then you want to become one.
Tl;dr I want off this ride.