I can't blame them for trying. Ultimately, you may be right that ego gets in the way. On the other hand, they could go on to win four titles together.
This hurts Lebron's legacy, no doubt about it. History will probably remember him as the guy who couldn't win a title on his own, so he went elsewhere to have D. Wade get him one. I think this solidifies him firmly behind Kobe in terms of best player of the era, and ends any discussion of "best small forward of all-time", let alone best player.
However, if Lebron made an educated decision that he cares about winning more than money and personal accolades, more power to him. I know we're all skeptical of that due to his ego, but in the end, I can't blame a guy for wanting to win alongside his genuine friends. You're right that he may not be ready for it, but on the other hand, I find it refreshing that a young guy is sick of losing after seven years (when "losing" means not winning championships, rather than being stuck on a lottery team.)