Ronaldo left the club by many reasons but most important, in my opinion, is their disrespect on him. They believed in Ten Hag and wanted to kick Cristiano Ronaldo out of the club in very disrespectful way. Therefore, Cristiano Ronaldo with his high ego, felt not only uncomfortable but very disappointed and he overreacted with this. I dislike the way he hosted an interview and revealed many negative things in the club, of course I am not naive to believe all things he said are true.
Some years later, Manchester United have fallen into a even worse crisis than when they had in very last months with appearance of Cristiano Ronaldo at their club. It's logical and evidence-based enough to say their blame on Ronaldo seasons ago was completely wrong.
You said it, but just so you know, who is successful now? CR7 and even won the Nations League, as some say: "The Finished gave them a lesson" and now we see a Ten Hag about to take over a team that for me is at a very high level than Xabi left it, I hope Ten doesn't ruin it, it's not that he will think badly, it's just that he applies a saying that says: "Create fame and go to sleep", it is difficult not to think badly of Ten Hag.