9 million is a very impressive number. Lets not forget the game sits on about 3.73m copies sold via physical alone on VGchartz. PC only gamers can only play it via digital distribution. But the real treat is GamePass, that is killing it for getting players to play there games.
State of Decay 2 - 3m players
Sea of Thieves - 4m players
Forza Horizon 3 - 9m players.
Well Horizon 3 hasn't showed up on game pass yet but since its going to be delisted in a little over 2 years they probably should add it soon.