LeBron is interesting because many have him neat GOAT status despite his lackluster Finals resume, he is a winner but not a great winner like other's if that makes sense. So he is considered a great player none the less and many feel that he doesn't need as many rings to validate that.

Still few expected him to win this one either way and I am sure historically going against a star studded team will be remembered as well, this wasn't just a simple Finals loss, it was an inevitable loss. This doesn't help or hurt him, just seen as a great player that went to his 7th straight Final and fell short to a superior team. He has enough backers that Finals record of 3-5 won't be too harmful.

For KD, it kind of helps especially getting FMVP since he is seen as the best player on a star studded team. I feel like in the future, it won't be as stressed as it is presently, like this ring will age better over time to the doubtful. The context being a great team lost the previous Finals, KD joins and as their best player leads them to a win, as it is now his team.