A lot of mistakes were made about halfway through the 360 era. They had a rather diverse portfolio back then, and some second parties. They could've done more to secure IP or studios but instead cut ties with nearly everything except for their pillars Halo, Gears and Forza. Worse, they doubled down on Kinect. This cost them as eventually they tried to focus on gaming again but they lost a ton of share by then and they basically never recovered. In hindsight I think MS should've sticked to their guns way back. The Xbox brand was in a good place.
Also, it isn't really on the nose but next to some obvious games such as Wukong, quite a bit of other games skip Xbox such as the Capcom collections, shmups and GG Strive wasn't available until after 2 years. This is a hardcore userbase thats willing to spend. 360 was actually the place to be on this front for a while.