You forgot to mention something more recent and verifiable, Irving couldn't even led the Cavs when Lebron was out during these last years. The Cavs record when Lebron missed games is atrocious to the point that it's even on par or worse than those older campaigns. Kyrie is not a leader that's for sure but he's trying to carve his own path, he's very young and I'm sure he can do it but he hasn't proven that yet.
Oh that's right why I missed it lol. One of the good example here is the Cavaliers worst record when Lebron James is out of the court. It was also being discussed this recent season because it was really noticeable that Cavaliers aren't playing well without (only) Lebron James.
But then things must changed now because Kyrie will surely left. And like I said, Kyrie must prove it's leadership next season to avoid taking criticism too much.
Something must happened internally with Lebron or who knows because I think he should have stay at least one more year. There's a strong case saying that Lebron will leave next year so that way the Cavs would be in full rebuilding mode (maybe forever if Lebron leaves again). Now it's all up in the air and the Cavs have to find a good trade for him without a lot of time or assets.
But well, we can't blame him, his heart is already elsewhere, he wants to start something on his own and he already won a championship. To me that's pretty respectable compared to Durant decision for example...