>>29651
It started on /co/, which was always a rather faggy board that actually prided itself on being friendlier and more open than the rest of cuckchannel. Keep in mind this was before SJWs. It started largely as a joke, a joke of male autists being like "haha, I'm into this girl's show!" Most of them weren't even serious at first, but were just doing it to try to get a rise out of people. But then some people were like "you know, actually it's not that bad." Their standards were low, you see. The whole joke was that obviously it was not good, so being not as not-good as they expected made it look better to them. But it was still very much about annoying others on /co/ and other boards, as they spammed it everywhere because they knew it annoyed people, and it annoyed people because they spammed it everywhere. Nobody else cared what show it was, but what happened was that people started spamming images of this show, so this was the show that became hated, and then more spammed because they found it funny to spam a thing people hated. And when I say spam, I mean things like, for example, if someone posted a single reaction image from the show, some other autist would come in and say "oh is this a pony thread now?" and then dump images of the show until the thread reached autosage.
Over time enough new people came in that didn't know or care about the origin. Many of them were in it for "the community" more than the show itself. It doesn't matter what the show was. They were "the fandom." The roving band of autists that goes from "fandom" to "fandom," because the real point is just being part of what they view as a "community." A lot of the bronies were probably into Homestuck immediately before, and maybe Avatar before that, and Sonic before that. After MLP, they'd be into Adventure Time and Steven Universe and Undertale. And yes, it's not all literally the same people. Some fall off, new ones join, but it's the same community. And yes, there are also those that are sincerely into the actual thing and not "the fandom," but those ones aren't the problem, and thus not the ones that get talked about. Those ones aren't the ones who made cringy Deviantart Sonic pictures in the mid-2000s, they're the ones who got hired to make actual Sonic games/movies/cartoons a decade later. That said, I'm not aware of if there are any bronies of this calibre. I find it hard to believe.
For an example of the attitude that lead to the initial growth of bronies, see this very thread. One autist with bad taste refuses to defend it, but instead revels in others calling him out on his bad taste. Now multiple this by about a million.