To be honest it's still surprising how much 3rd party support Xbox still gets despite the fact that it's clearly falling off hard at this point and is now selling Wii U numbers while the Switch/Switch 2 is likely going to sell 3-4 times more than it and still misses out on a few big titles.
I guess even with a 30M install base, the install base still heavily supports 3rd party games enough for a profit. Or it legit could just be the big brand name & mature image of "xbox" carrying the idea to 3rd party developers that its still a must to release their games on it, while Nintendo despite the install base still has that stigma of being too family friendly and different to be considered as a place for 3rd party game.
To be fair, it also might just be relatively easy and inexpensive to port from PS5 to Xbox to where developers wont feel much expense in doing it despite the lower install base







