They lost the Hearts and Minds with their absurd drm demands, before they even launched, they completely missed the train on the TV TV TV hdmi in thingy.
And they have not and imho will not convince the gamers that kinect 2 adds value worth paying for. Which leaves them with a out powered expensive console that only can compete on price.
And they are behind on the included services as well.. E3 will really have to be mind blowing in order to regain ground, and Sony will have screw up badly on their E3 as well.
MS was certainly looking to doing 4 or 5 things at once with the "ONE" and they all seemed "synergistically" support each other. On paper the strategy was bold ... reminds me of "A Bridge Too Far" ;-) ... and based on what, say Apple does when it comes to their products, it also seemed quite doable. Now for such a masterstroke to be effective a certain level of dissociation from reality is sometimes needed to get over the "It Can't be DONE" mentality that get's in the way of getting things done.
Unfortunately they incubated in this "Can DO" bubble for a bit too long. They were crafty in leveraging technology and trying to create a sum greater than the parts but they ended up too ahead of the curve in some respects and a little too late to the party in others. This tension along with the price is making getting traction this generation more difficult than they were expecting IMHO. Based on the price and the money spent on exclusives early on in the process they were expecting to be ahead of the Sony by a bit by and were not expecting to look back at them again ... ever. Now that that strategy hasn't born out ( like a few other strategies already mentioned ) they only have one or 2 more moves left besides sticking it out and playing the long long game.
Price cuts stops the slide but hurts the bottom line. Doubling down on the Kinect/New Tech/TEH CLOUD may not stop the slide and will hit the bottom line anyways AND won't be a factor for quite some time assuming that they don't already have something waiting in the wings at E3. Otherwise it is steady as she goes ( Halo X and other exclusives to keep the faithful ever such ) until a cost reduced version ( diskless with some reworked architecture ) becomes feasible. Now a cost reduced diskless Kinectless version at $329 or maybe $299 could be crazy popular ( I'd get that one without another thought ) but if such a creature were to rise it would be with say Gears of War timeframe. I think Halo 5 will still be the final line in the sand for the full featured machine.
I don't envy them but I do enjoy watching them stretch themselves and hopefully come up with something interesting.