Well he has achieved what he intended to do when he started racing, I always think retiring at a high note of your career is always better than lingering in the sport until no one wants you (for reference see M. Schumacher); Especially so when you no longer enjoy what you are doing like he stated.
Like you said it is better to say he is crazy to retire when he is still sooo good at it, than later asking why is he still in the sport when he is no longer competitive.
“You Either Die a Hero, or You Live Long Enough To See Yourself Become the Villain” - Harvey Dent :giggle