the issue is that really talented people a lot of times lack heart...because they have been able to get by for so long on talent alone.
While i dont disagree, there is alot of arm chair psychology when it comes to sports especially polarizing figures like Lebron. Sports journalism or should I say tabloids basically function as media rags to push narratives and sensationalism. Used correctly it compliments writing/media well, but the majority of media is based around that fact almost solely. So as result we have the Skip Bayless type echo chamber that reverberates in sports culture and becomes part of the fan collective group think.
Has Lebron failed on the big stage sure, is it due to him having no "heart" or being scared only he truly knows that. I would hope since hes been doing this since a teenager he would know how to harness anxiety in tense moment appropriately. If I had to guess what is been the biggest culprit is he allows himself to "think" about tense situations instead of playing on instinct and anticipation as he normally does and what makes him Lebron.
He has the gift like J.Kidd or Nash to see moves/plays ahead, but I think he gets in his own way sometimes cause he overthinks and blocks the natural way think flows for him. Whether that is because hes overly concerned about criticism or failure, only he knows. But I dont believe its fear in the sense of not wanting to be in the moment and wanting to remove himself, but just the incessant overthinking.
The say some people with his type of savant type gift for things can be overly critical of themselves, you see signs of that with him with how much he tinkers with his shooting form and free throw form. Even when he find something that works, hes quick to change to something more familiar once he has a few mistakes with the new form.