You know it's not as if Medvedev isn't familiar with red clay, he's lived in the south of France for years and the Academy he attended has plenty of the red dirt to practice on. As Front has previously pointed out, he's had some good results in clay Masters. It' seemed more psychological/mental with him, and I'm sure Medvedev had the light bulb moment early that HC ideally suited his game and would be his bread and butter.
Springs to mind Agassi who famously said (like Lendl before him) "grass is for cows" and later made the adjustments mentally to enjoy
Wimbledon and grass court success. Agassi came to the realization that certain aspects of his game (hitting the ball on the rise, return of serve prowess, etc) were strengths on grass, as hopefully Medvedev now has come to a similar epiphany regarding clay.