You have to focus, Xbox done bad because of the pre launch PR, even if they corrected everything but Kinect and princing (well and in here Xbox fans were very defensive of Kinect, even more since it brought a lot of sales to X360 late life) which took them like 6 months to correct. So in the first 2 months it sell almost equal to PS4, in the final 78 months it was always cheaper than PS4, but the problem was those 4 months in between where it was more expensive.
Oh I agree. But what you have just described is a totally different thing.
With the XB1, everything leading up to its launch, and then its price all conspired against it. So even though the Xbox diehards would still be enough to carry it through the launch months, 3+ months after that things would start leveling off, or better put after it has sold through to its most loyal base, you start seeing the sales it would have based on the actual merits of the system.
If MS had 3M XB1 consoles available on launch day, they would have sold all 3M of them.
And thats the point I am making, sales during the launch window aren't indicative of overall sales performance. The people that buy-in at launch or at least an overwhelming number of them are the ones that would've bought in no matter what. And every platform has a different number of those people. Eg. I believe that if sony has 10M consoles at launch, they will be able to sell 10M consoles in the first week on the market. As long as its not priced at $599. MS would probably be able t achieve the same feat with around 5M consoles.