I think most people had that teacher that was crazy hot, sometimes a substitute teacher that appeared and was not only fucking cool, but absurdly hot, that kind of stuff stays with you and then VOILA! Shotacon becomes interesting because it takes you back to that I guess. Or! hear me out... people have random fetishes and they like what they like without specific reasons.
I had a friend who had a hot mom, like an actual hot mom, and she adored me too so that didn't make things easier for me. She was, of course, a normal woman, so nothing happened. Maybe I got it from that, maybe not, who cares anyway?
The age gap, the taboo, the fact an older woman is allowing your inexperienced self to feel her that way, maybe the idea of being taken care of nicely, the coming of age classic story, the moment that could have been in your youth but wasn't. There are many reasons to it really, but some just like it.
I will always disagree with the logic of "You like loli hentai? Must be a freak pedo LOL!" That's just absurd and mean for no reason. Also kink-shaming and then the double-standard is a real low, especially considering where we are. That's like "You like violent games? Must be a serial killer!". People don't actually do the things they do virtually, some even find it disgusting outside these boundaries, not because they feel guilty, because they are normal humans with functioning brains that know some things just belong in fantasy.
Lately I've seen people say "If you like a hairless pussy you're probably a pedo, real women have bushes!". I'm like "what the fuck is that logic now?" So I guess people just like to point fingers and shame others whilst assuming the things they do are completely fine.
Fucking long post again... I can't control myself!