In fairness, that would be anyone's career-defining moment.
But I do get your point. I still think Xbox under Peter Moore was learning how to get very good at shepherding Xbox-only games on the console. There were smart partnerships with Sega and other companies (the Sega partnership actually is what got me to go Xbox after the Dreamcast died). If you recall, they had exclusive working relationships with Ninja Theory (called Just Add Monsters at the time), Double Fine, and Obsidian all alike. Kung Fu Chaos and KotOR II are Xbox exclusive, and Psychonauts was going to be Xbox exclusive until Microsoft dropped it late in development and Double Fine had to scramble and find a publisher.
They just did not continue to develop these relationships. From Mattrick on to today, Xbox leadership has had damn near zero video-game-related ideas. Sometimes I wonder if Phil Spencer even likes video games. Isn't there something Spencer would love to play that isn't already someone else's IP? Throw some money at something interesting, damn. They haven't really done that since they were the kings of the early indie-on-console scene.