This is the reason I never buy into the 'United don't back the manager" nonsense.
Every manager we've had since Fergie, with the exception of Ole, has signed one or two players who have played under them in the past. Players we normally wouldn't have signed. LVG was obsessed with his dutch core so much we were linked to the likes of Martins-Indi, Jose wanted and got Ibra and Matic. Then there are those they targeted at their previous clubs or were known to admire e.g. Mata with Moyes, Mhiki, Bailey with Jose and Maguire, Sancho and Ronaldo with Ole.
Doesn't take much to realize that managers still get a very huge say in who the club signs, infact I'd wager our scouting teams get overuled more often than not because the club wants to be give the manager the ultimate power.
Now that in itself is not a bad thing, but given our managers have sort of averaged two years, and we are not consistent with the caliber of manager we hire, this approach is both costly and unsustainable because we will always be in a state of 'rebuild' as each new manager comes, asks for new players for a different play style and considers the current ones deadwood.