Games like Life Is Strange and Animal Crossing are hardly niche; Animal Crossing is a massively successful multimillion selling market leader interior design game and Life Is Strange is a critically successful drama that made way more money than anyone writing the sub-Degrassi high script deserves because the market constantly craves for an influx of barely interactive "narrative games". These games have massive commercially viable hooks and have massive playerbases because of it.
Sell Life Is Strange to me ten years ago. That game would NOT be selling what it is now and that's a fact. Life Is Strange is definitely niche. It's a boring game - on purpose. Shenmue is also a boring game - on purpose. Ten years ago, boring games that involve the daily lives of teenagers were not a thing and adventure games backed by companies like Square Enix were, for all intents and purposes, dead.
Animal Crossing had an audience before, but New Leaf took it to a whole new level. It is definitely niche. Just because it's successful does not mean it's not niche. It has just managed to fit into that niche comfortably.
Either way, you ignored my other multiple examples.
Ys was a a total bomb before heading to Steam. I bought Ys III for psp and it was a complete bomb. Putting it on Steam invigorated the games sales. Now they're up to like, Ys IX? And a big part of that is Steam.
Valkyria Chronicles sold GANGBUSTERS when the game was released on Steam when it did only modest before. It's a strategy rpg. Strategy rpgs are niche.
A big part of the reason the Japanese games are so successful now is because of Steam. It has expanded their audience ten fold and has done extremely well for niche games.
Then there's games like Stardew Valley. A game like Stardew Valley/Harvest Moon is niche and that game has sold enough it could afford its own island by now.