I think you hit the nail on the head here

Lebron's teammates aren't really empowered or prepared to make those sorts of decisions
I mentioned in another thread - you have to practice these late-game situations relentlessly so that decisions become muscle memory and everyone is on the same page. Under enormous pressure, and with all the crowd noise and cameras flashing, its real easy for someone to blank out. You really don't want to have to rely on someone
thinking in these situations. Especially not JR Smith

The military does that sort of training to make sure soldiers can still function effectively in high-stress, life-or-death situations. Doctors as well. Well-coached sports teams do it too.