Different issues, different reasons.
Some of them are joining the Black Lives Matter movement like this one.

https://clutchpoints.com/lakers-news-dwight-howard-supports-kyrie-irving-refuses-play-basketball/

Some have issues the way management of Disney World is doing things.
Security, test, and staff. Those kinds of issues.

They all agree back in March and April until George Floyd's questionable death in the street.
Some players are shaken and others are trying to be in the middle of the racism issue.
The most fearful thing that could happen if this racism goes inside the players and management.
I am sure they will be times it will be discussed and there may be a misunderstanding that would lead to a bad end.