There’s also the whole “Ubi refused to allow it on Steam because they didn’t want Valve to eat their cake” side of things. Ubi believed that Mirage would have enough market pull for them to only release it on their internal Ubi store. It also has Denuvo, which many PC players despise. So nobody on PC bothered to play it, and it was only noteworthy for console players. Mirage only recently released on Steam, (I think around Halloween of last year?) but by that point any marketing that was done for it is old news and players have moved on. Ubi seems to have learned their lesson, because Shadows is releasing on Steam at the same time as the rest of the platforms.