

It wasn’t their money to spend.
Sure it is. That’s how a free market works. You are free to engage directly with indie developers on itch.io etc. It’s not your call to make what others do with their money. You don’t see me fuming with rage just because you spend your money on different games market places.
Microsoft controls both Xbox and Windows. If Valve can make Windows games compatible with Steam Deck, Microsoft can make Windows games compatible with Xbox.