Something it doesn't seem many people are taking into account is Nintendo and the Japanese market.
Steam gamers in Japan are a niche within a niche. While Sony has done a decent job of pushing indie games in the west (or at least used to) they never really expended much of that energy in the Japanese market. Nintendo on the other hand has the Switch, which is on track to beat the total install base of the PS4 in the next year or two. Unlike Sony, Nintendo has been doing an amazing job of introducing indie games to the Japanese console market through special events and videos that explain these games in more detail than more western-targeted material. As the PC market for many of these games in Japan is incredibly minute, the Switch is basically the ONLY place that many of these games are going to be played by Japanese consumers; as such, a successful Japanese console, a remarkable effort by Nintendo's domestic marketing team, and what amounts to basically the only place to play these things (even if some literally are also available on PS4 or mobile), and you have a recipe for indie success in the Japanese market at levels heretofore unseen. So while "Nindies" sounds remarkably twee to those in Western markets, Nintendo=Indies is not an exaggeration when dealing with the Japanese market.