#2 Power Play
Zidane met with the Madrid hierarchy including Perez before he announced his decision to resign and it has since been reported that Zidane and Perez didn't see eye to eye on the transfer targets which forced Zidane to resign.
Madrid is a club where Perez and the superstar players such as Ronaldo, Ramos etc hold all the cards with the manager having little to no say in everything.
Zidane beautifully managed the egos within the squad and his handling of Perez was exceptional, but it eventually proved too much even for him to the point that he felt that he couldn't take the pressure anymore.
One of the reasons why Klopp was not even considered it that he will certainly demand more say in transfers and if it's one thing Perez hates, it is giving up power.
Pochettino and Allegri have the final say when it comes to transfer targets at the respective clubs and are more involved in the day to day running of the club.