The one thing I would ask is given how Moyes was booted for underperformance, and Van Gaal was booted for underperformance, at what point does the revolving door stop and they actually back a manager properly?
When one doesn't underperform, same as any club.
Sticking with a manager who's doing a bad job doesn't work. Anyone coming into United and spending £200-300m should be delivering very obvious improvements either by winning things or playing good football that shows something's being built.
Managers like Klopp or Pochettino have delivered obvious improvements in player performances and style of play without actually winning anything - those are the kind of managers you stick with and hand money to.