Think you're right with Ole tbh. they're in a right pickle as a club as have a few players De Gea, Rashford, Mata, and Bailly all coming into the last 12 months of contracts. If they lose De Gea and Rashoford in a year whilst having a merry go round of managers then I can only see a long struggle to get anywhere near the top again. Even with the dosh they have you gotta get a good manger and give money and time, all three of Pep, Poch, and Klopp had a tough first season and took time to get going. There's just so many good teams in the prem now that you can't epect to get a new manger spend 150 mil and see positive effects. Lose Rashford and De Gea and they're gonna struggle, the fans will be pissed right off too.
Rashford really needs a manger that's gonna coach him now too as he's no better now than he was 2-3 seasons ago really. Still quite one footed, poor in the air, and one dimensional. Poch could get more out of him for sure, as would Pep, Klopp, and probably Emery too. Think he'd do well to get away from Pogba and Lingard as they just seem to fuck around all the time.