Ole's administration was a shining beacon of the chasm that exist within the football structure. First of all Ole should have never been made manager of Manchester United. United are a sleeping giant, there are plenty of departments that are failing (ex fitness, leaks etc) and we expect too many things from a manager (he needs to cover the role of coach, manager, sporting director and head of recruitment). Thus I struggle how one whose only previous experience at top level was tanking at Cardiff could succeed in that job. Anyway many of the issues we've seen during Ole were present before and after still present now. For example we sign the wrong players we spend too much on them and we give them silly contracts, our fitness is not up to scratch and we leak like a sieve.
So what went wrong? Ole inherited a Mourinho's team ie a team built around a deep line and playing counter attack football. It was apparent even from that time that such tactic was in the way out. Unfortunately due to a list of inexperience and incompetence at both managerial level and DOF level we noticed that far too late. Thus we ended up bringing players like Maguire and AWB whom while good for that style of football were unsuited for modern football. Add that to our inability to negotiate advantageous deals and our inability to do adequate research on whether players have the right talent/character to succeed at United (ex Sancho and VDB) then no wonder why things degenerated the way they did.
What I do blame Ole for are
a- his lack of discipline
b- the fact that we signed a RW who wanted to play LW
c- the fact that he left for a holiday to Norway when the ship was actually sinking.
d- he seem to have promised everything to everyone (Hendo, Lingard) when he knew very well that it couldn't be done
There also reports of him refusing to implementing new ideas from McKenna and Carrick that could add to that list as well. All of that are damning irrespective of the manager's experience and/or character. Its undeniable that United have far more problems during Ole's reign that prior. Again, mostly not his fault.
That doesn't take the shine from him as a person and as a United legend player wise and I wish him all the best in his future endeavors.