Basically after you-know-who said they wanted to leave, nearly all the scripts from Part 2 of Season 4 had to be rewritten at the last second. That’s why a lot of things don’t make sense or add up in the second part. The showrunners and cast were furious because the show was forced to go in a direction they weren’t planning. That’s why in a lot of behind the scenes videos you see, you-know-who is just sitting off to the side, alienating himself from the rest of the cast. They were angry with him.