>>9684733
Honestly, the very main reason I see is Touhou honestly.
Touhou fangames began somewhat simple, but over time they've escalated. We've got puzzle games, fighting games, shmups, RPGs, platformers, and even more. Touhou has dozens of games which are pretty much "X, but with touhou".
Dyna Marisa, Touhou Mother, New Super Marisa Land, and more.
This has pretty much spread Japanese indie games to every genre. The sheer fact there are 3 Japanese doujin games based off EDF is an example of this.
Whereas with the Western scene, the only thing with a fandom close to making something like that happen is MLP, but it's already too late now. I don't like MLP, but from what I've seen, they're making a fighting game, a cart racer, and even a Silent Hill game, I'm not kidding about that last one.
If MLP came out years earlier, the Western indie scene might be incredibly different, it would also be probably full of MLP games. Either way, the situation's not that great sadly.