Yeah the mobile part is irrelevant to me too. At least for now. Maybe it will change with cloud gaming, but we are not there yet. And I don't see it becoming a real thing on mobile to be honest. But for the PC part, without talking numbers (because of course most are for business as you said), we can't ignore that PC gaming has regained a lot of attention in the past years.
Honestly, I don't know if that's a good strategy to "abandon" some Xbox console sales to re-enter the PC gaming market. I think Microsoft did their maths and conclude that it would be good for them. At least it doesn't seem a completely dumb strategy to me (and, as a gaming PC owner, I can't say I'm not interested...).