There is a laundry list of reasons, but here are some big ones.
1. The reveal. The reveal and initial features of the Xbox One were an unmitigated disaster. Even some big Xbox fans were disgusted and vowed to jump ship to PS4.
2. Price. The Kinect 2.0 was initially bundled with all Xbox One consoles. A lot of people had no interest. You were paying $500 for a console that was less capable than the PS4.
3. Lack of true exclusives. Very few games are truly exclusive to the Xbox One. And more importantly, the first-party output they had were not received as well as the Xbox 360 library.
4. Lack of Japanese titles and exclusives. I know the Xbox consoles are a non-starter in Japan. But even the Xbox 360 managed 1.66 million units. The Xbox One has only sold 0.12 million units in Japan. It'll be lucky to reach 0.15 million in Japan before it's discontinued.
Lifetime Sales Predictions
Switch: 161 million (was 73 million, then 96 million, then 113 million, then 125 million, then 144 million, then 151 million, then 156 million)
PS5: 122 million (was 105 million, then 115 million) Xbox Series X/S: 38 million (was 60 million, then 67 million, then 57 million. then 48 million. then 40 million)
Switch 2: 120 million (was 116 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima
