Among Us is an interesting one because it flopped on release and only exploded later when people realised the streaming potential it had, which brings in another factor: costs. I'm just speculating, but I reckon if you looked at most surprise hit video games you'd find almost all of them had small teams and modest budgets.
No modern AAA game can afford to fail before it succeeds, even a lot that sell millions of copies are still considered failures because the costs they need to recoup are so high. Putting that kind of money behind a live service game is insane; even if Concord had been great it would still probably have been bleeding amounts of money only Microsoft could tolerate.