Ole did a great job at Molde, and changed the club forever, breaking records and attracting the best talent for years. And the club is still reaping the rewards. His successors did great with what they inherited for a while, before slowly fading, as proven again this year.
A disclaimer is that I hate Molde with a passion. They're literally the team I hate the most in the Norwegian league, alongside Brann and (now relegated) Lillestrøm. I want to say that they've done bad, and that Ole didn't perform or lost the plot or whatever, but after all the pain and suffering he's cost me as a fan of another team, it would require some pretty drastic mental gymnastics to come to that conclusion.
He did some morally questionable/despicable things while in charge, and you can certainly argue that he lost a lot of respect from a huge part of norwegian football fans (and the general population), but that has nothing to do with his performance as a manager. You can point to his shady dealings with agent/friend Jim Solbakken, but again, a different thing.
There are so many things you can say about Ole as a manager, and even as a person. His time in Wales, his results with us, his tactical ability, his persona, his moral. There are thousands of arguments to back up any negative opinion about him. His results and sporting legacy as a manager of Molde FK is not one of them. He didn't run out of ideas at all, he got a job in Manchester instead.
Of course, this is all my own opinion, and everyone is free to have a different opinion. That's fair, expected and respected. But if that opinion is based on nothing at all, I think the opinion is less valid.
Edit: And no, he's obviously not the best manager the Norwegian league has ever seen. That would be Nils Arne Eggen, by quite some distance. He's the best norwegian manager ever, and probably one of the european greats (top 50, maybe?).