I am reminded that the old House Kurita sourcebook mentions that most people who could be excellent MechWarriors never get the chance, due to being born to some peasant family instead of the nobility. It could be that not only was Stone in the right place at the right time, but he also had the right brain to become a noted MechWarrior. This would help explain his political success; since most of the Inner Sphere's rulers were themselves MechWarriors, they would've been far more accepting of him than, say, an infantryman who managed to lead a prisoner revolt.