I have done all the investigating I need to do. Lifelong fan, read all the books on Clough, watched all the TV where he's discussed his time at Leeds, virtually every Leeds Utd player's autobiography's from the 70's, watched numerous documentaries about Leeds in the 70's and listened to my Dad who went to virtually every Leeds game played for 40+ years. I am coming with a little knowledge on the subject.
First Clough has systematically criticized Leeds for a number of years previous to joining them as manager. Not only had he branded them cheats, but individually called members of the team cheaters, dirty bastards and talent less. He always disagreed with how Leeds played the game and was not backward in expressing this opinion.
Don Revie recommended Johnny Giles as his successor, but for reasons that will probably never be fully understood, the board chose Brian Clough. He arrived at Leeds and immediately alienated the majority of the players who were told that they had only won their medals because of their cheating. He further deepened resentment by selling key players and personalities that were part of such a great club within days of his arrival.
He admitted in his books and in many interviews later on in his life that he made many mistakes at Leeds. Changing things too fast, the way he treated the players at the club, dismissing the whole teams previous achievements didn�t go down well with older players, bringing in too many players in key positions (Duncan McKenzie, McGovern and O'Hare) who were just not good enough.
I don�t really blame Clough; I blame the board for hiring such an inappropriate person.
No idea why Clough took the job of a club he so clearly disliked and hated.
And yes anything outside the top flight is lower leagues.