The split is usually not a multiple. There are people with computers, and people with xboxes. If there are that few people on steam, there are probably a similar number on Xbox. Not 10x or 100x, and at least 100X would be what you need for that game to be worth further investment.

They wouldn’t.

Only people without GamePass subscription and no desire to get it for even a month or two would buy the game on Steam.