Sounds like a breakdown in his relationship with United's board more than anything else. They have broadly been heading in the right direction for the last 2-3 months and I could have easily seen them finishing 5th-10th with the way the middle pack have been playing this season. From there, I think 4th was reachable within the next 1-2 seasons.
Now they have to start the project all over again. It's mostly likely to be Maresca - although his tenure at Chelsea ended largely for the same reasons (control, backing), so maybe not - but I wouldn't be surprised if it's the trio of Fletcher, Carrick, and Solskjaer running things again until the summer. Think this is a really silly response to Amorim's presser.