LeBron is one of the greatest athletes in the world. Normally, basketball players his age would have retired years ago, but he's still striving to become a champion. He still has the athleticism of a 20-year-old, and his game is still incredibly high.
That's why he's one of the most respected people in the world, and it's incredible that we still watch him on the court. He's achieved more than any other basketball player

He hasn’t had a serious injury, that’s why he’s still active now and still leading his team. Other players weren’t as lucky, like John Wall, after being sidelined for a season he was never the same again. The only one I can remember who bounced back strong was Paul George, he even landed a good contract after the serious injury he suffered.
Injuries kill careers, just look at Derrick Rose if you still remember. So let’s just hope LeBron stays healthy so he can play more seasons.
Lebron is investing a lot on his body, that's why up to his 20th season, he still can dunk and move like he was still in this prime. And most likely that is the reason as well, he is very careful on what he put in his body, just like the other great player in Tom Brady. So he might have a chef that personally cooks for them and then with the adjustment of sports medicine, he is healing that body with hyperbaric and red light chambers as well as cryotherapy.
@AbuBhakar - as for the discussion of the GOAT, it's very hard to compare era's to era's.