What if LeBron calls Kyrie personally, and asks about his time so far in Boston, especially dealing with ownership, Danny, and coach Stevens. Maybe Kyrie didn't necessarily have an issue with LeBron, but more so the relationship between LeBron and the power that came with "we'll do what ever you want LeBron" attitude that the Cleveland team gave him. After all, it was the Cleveland team that pushed Kyrie aside when the opportunity to sign LeBron was a reality.
What if LeBron just misses playing on a team with other good players and a stable organization, like his time in Miami. And explains to Kyrie that he understands that he (Kyrie) is the leader of the team, and is willing to sacrifice by taking the full MLE.
Obviously, the chances LeBron signing with Boston are slim to none, but it is a fun exercise. I feel that everyone just assumes that LeBron and Kyrie have no relationship anymore and thought that this could be a curious angle of how LeBron might end up in Boston.