SAF relationship with his employers was unique given tenure and retirement rather than being sacked, but his role in choosing his successer should have been minimal.
It's not a managers job to pick his replacement or plan for a future without him. That responsibility should lay squarely with his boss and boss's boss. In SAFs case that was Gill and Avram Glazer, complicated by the fact that Gill was also leaving.
We'll probably never know the real truth why Moyes was appointed, but if it was because the board simply took SAFs advice without any other due dilligence, that is a mahir dereliction of duty, and the fault lies soley with the board.