Gaming

I don't think it was a factor at all, they are both very very close in terms of CPU power (the series S is the same CPU run 200mhz slower), which MS did so any game could easily be run on both by just dropping some graphical fidelity and calling it a day. The fact that they didn't even try to have some kind of unlocked or 40fps performance mode on the X suggests they are very CPU bound, and the PC system requirements reflect this too, requiring at least a 6 core CPU. I think a lot of gamers with 4 core CPUS are going to be screaming about how the game is "unoptimized" when the reality is just that there's a lot of stuff going on, and yes, 4 core CPUs are starting to become practically vintage at this point.

Gamers always want to have their cake and eat it too, if you expect games to always get bigger and better then expect to need a bigger and better computer to match.