You're confusing 1) Ole the manager (i.e his quality and ability) and 2) Ole's approach. Ole as the manager was just bad; 3 years of some ups but many, many downs. Ole's approach is debatable in that firstly, you can't use the GOAT manager and use that a baseline to say it works, especially as Fergie started as an elite coach and only got 'hands off' because he was Club. Secondly, if you look at all the top coaches across the leagues and in past seasons, who have had sustained success, they are all very involved in the coaching. The outliers either have had vast amount of experiences (e.g Ancelotti at Real Madrid) or there was some other extenuating circumstances (Guardiola/Zidane taking on a demotivated but highly talented team with a GOAT player in a 2/3 team league).
As for the 'if they had better coaches' argument, I would say this only works if the manager themselves knew more/had the ability to still make the 'right' tactical calls and actually get the players to playing how they want. You can't just palm off responsibility as 'the coaches wasn't good' enough. It comes top down. It's why managers like Gerrard (Beale) and Klinsmann (Low) failed as their assistants knew more/were better/whatever you want to call it. This may happen with Ole as McKenna and Carrick may potentially prove themselves to be more competent from a coaching perspective. There's a lot more nuance of course but in its simplicity, it's all on the manager themselves being 'good' enough or not. It's not about the 'approach'.