In the documentary Microsoft admitted that Xbox was dead after the Xbox One reveal, Mattrick resigned by email before it launched and everyone thought it was over.
Marc Whitten, in charge of Xbox products (i.e. hardware) shortly left after Mattrick did and joined Sonos.
They searched around for someone to lead the Xbox team and when they couldn't find anyone on such a short notice to replace Mattrick and Whitten they appointed Spencer as head of Xbox because he was leading Microsoft Studios making the games at that time.
Microsoft figured the best way to salvage Xbox was to appoint the guy with the most experience in gaming and basically made him head of 'everything' that was dead in the water at that time like Xbox Music, TV, Live, Video etc. etc.
Spencer went to work by shutting down Xbox TV Studios and all the other stuff that was 'not gaming' and immediately ordered the hardware team to start work on a next-gen machine that would become the Xbox One X.
Phil Spencer is a gamer that could rise up because we called out Microsoft's TV bullshit
