Sure, they've done it before. But if it's Embrace/Extend/Extinguish, why did they wait for so long to do this? What is it about Linux in 2016 that makes it a different threat to them than it was 5, 10, 15, 20 or 24 years ago?

Isn't it far more likely that this is simply another execution in their recent opening up of their platforms to developers?