Shouldn't the sales be greater for an established developer? Not saying they need to post Rockstar numbers but 2 million sold after nearly six months doesn't sound that great. It is selling considerably less than Horizon, which sold 7.6 million within a year. So maybe 3 million overall by May 2019.
At least the way I understand it is that a large majority of game sales come early on before a gradual or sharp decrease.
I have no idea how well new IPs from Xbox sell. I can't even name any apart from Sea of Thieves and ReCore, haha.