Celtics were fine last season when Kyrie played 75% of the season before he got injured. The difference this season is the inflated egos that came with the young players making it to the conference finals without Kyrie and GH.
nothing wrong with ego Michael Jordan and Kobe had tons of it. The great ones do. Perhaps the problem came from Kyrie the self-appointed leader not knowing how to deal with or nurture those egos.
I think part of the issue was that Kyrie probably lost some credibility because he missed the postseason when they made it to the ECF in his absence. Prior to that it's easier to be the clear leader because they were all kids. But then they made the finals...without him or Hayward, the 2 biggest profile players. Hayward came back, played like trash, so his credibility was really worth zero, and Kyrie couldn't really come in saying "listen to make the finals we need to do a, b and c" because, well, they made the finals without him. There could've been a "chillout Ky, we've been there, we know what it takes, you don't need to tell us" type mentality, particularly at the beginning of the season. Confident young players who overachieved and have the world at their feet. Mitch Albom's book "The Fab Five" about the Michigan freshmen back in the early 90s tells a similar story of vets vs young players and the coach (Steve Fisher) who struggled to keep it all under control.
That's probably when he started to become overbearing, make snide comments in the media about the young guys, etc. Because he wasn't like that at all in year 1. He lost some of his moral authority and didn't cope well with it, and responded the wrong way. Certainly not absolving him of any blame, he still didn't handle it well, but I could see it going down that way.
As for Hayward, I don't think they respected him at all, not in a basketball sense anyway. And that's a fair feeling - he hadn't earned any of their respect, so his voice as a "veteran" probably didn't mean anything.