I wonder why the top players in tennis (Federer, Nadal, Williams) are lasting longer than is traditionally the case? - Better nutrition and recovery than previ

I wonder why the top players in tennis (Federer, Nadal, Williams) are lasting longer than is traditionally the case? - Better nutrition and recovery than previous generations? - Unusually dominant top players, resulting in easier matches and less wear? - Playing styles that result in less wear and tear? - Upcoming generation not as good, so not challenging them?