Problem is: Mou lost the confidence/support of the board after the Sevilla fiasco, and how he dealt with it.
When he realized it (too late, his fault) in July-Aug, when he didn't get the new signings he wanted, he made this public, bitter statement "Get ready for a terrible season". That basically broke the squad and the air became too toxic. 2018-19 season ended in Aug, make no mistake.
Ole did what he could and actually made us reach "Top4 contenders" status. We could have easily ended up 3rd this season. The awful results of March-April are the fault of the players, period. Mou was the one to blame in Aug, the franchise players (DDG, Pogba, Martial, etc) are the ones to blame in May. And, like Mou, they have to go. Full circle.
Summer 2019. Time to rebuild the squad for good.