He's clearly done well to turn things around on the field, can't even argue otherwise. I do think a lot of it was just the classic new guy bounce though. Different face, different message, fresh start which have given them momentum and the results speak for themselves.
The players who were just relieved he wasn't Mourinho now have to accept he's the new guy permanently now and they could be sold in the summer. They may need to extend their contracts, he may sign players to replace them and that dynamic has now changed. The novelty of him will soon wear off and I honestly think it'll go completely to shit in 12 months time. It virtually never works out appointing a successful caretaker. This is no different, its a classic mistake.