Xbox One also came off of the success of 360. It may have still finished last, but it was a close last. So, Xbox still had a lot of fans at the time. Even the terrible reveal and horrible policies, which many they quickly reversed, couldn't kill it. What really killed the One is that PlayStation was back to firing on all cylinders, having the better HW and games output, while Xbox kind of just gave up midway through the gen, releasing fewer (and mostly mediocre) exclusives.
So, XSX is releasing after a failure, with fewer fans, and the same horrible management and poor games output. They even launched the system without any real big exclusives. Add in their games are now available on PC and GamePass Day 1, with many are now coming to PS5 and Switch, there's just no reason to own an Xbox. Sales are just going to continue to crumble.