In response to your final point, perhaps he's willing to give them time? I suspect he'll prefer to stay loyal to the current coaches, given their past connections to the team, rather than look for another coach.
As I see it, a manager has four main areas to oversee:
1) man management
2) instilling footballing philosophy, and integrate into tactical preparation
3) coaching players to fit with point 2)
4) finding players that can be coached to fulfil point 2)
Managers can outsource parts 3 and 4, but needs to be in charge of at least parts 1 and 2. Most managers seem to do 1), 2), and 3). By all accounts, Ferguson did 1), 2), and arguably 4).
Ole's man management seems to me to be his forte. His tactical acumen is open to debate because we simply don't know from our position whether his footballing vision is poor, or whether he has good awareness but has coaches that are struggling to implement it. I think most would agree that we have decent players who ought to be able to follow instructions. People might point to Phelan and say he ought to know what to do, but apparently he also doesn't take charge of training. If Ole were sacked, would the next manager keep hold of the current first team coaches? Very unlikely. As Neville would put it, we need the 'best in class' coaches to let a relative novice manager focus on points 1) and 2), and we need Fletcher and Murtough to be brilliant at 4). That's the only way our performances can gain some kind of consistency. In my opinion...