He really became delusional and thought he could turn every talent into a superstar, because Müller and Badstuber were instantly successful.
I love that we got him, he turned the club around, gave us a longterm plan that was worth following through, teached all the players some basics they clearly didn't know before (mostly technique, positioning and movement). He was the right person to make necessary but unpopular decisions, I'm thankful for that. But I was glad to see him leave. Within 8 months in the new season, the whole squad was in disarray. Everyone was fighting with each other, Robben choked Müller on the pitch at the end of a game, Ribery punched Robben at halftime. Everyone hated playing football all of a sudden and van Gaal's stubborn tactics were found out and countered by every decent manager in the league. The amazing football we played at the end of his first season was gone. The basics were still there though and Heynckes could build an amazing team on van Gaal's work.