#1 is kind of ridiculous. The team was never affected by Hayward or Kyrie not being on the bench to cheer on the team. And Kyrie had surgery on the day of game seven that was scheduled way before anyone thought the Celtics would be playing a game 7 of the ECF. Cancelling the surgery most likely would have meant Kyrie rescheduling it much closer to the start of the 2018-19 season and affected his ability to get as ready as he was for this season.
#2 Yeah all the young guys are struggling to fit in new roles where they aren't emphasized as much. You're 100% on there. Yes, it could be ego, but I don't think it's that. I think it's more those three players were playing roles last year that they have been playing their whole lives and so excelled in them. They just aren't used to maximizing their games in much more limited roles.