Another of my Geese theories: In FFS one of his win quotes goes something like, "The immortal Geese is about to take you to a very hot place indeed." To me, that kind of implies he cut some kind of deal with Satan, or whatever dark power you like, not to perish after his fall from Geese Tower, and is now something more than human, acting as their agent, collecting the souls of the fighters he defeats to pay off his debt.
Kind of going off on a tangent here, but, I feel that Rugal's use of the Reppuken, but NOT the Raging Storm, implies that he tried, and failed, to master Geese's SDM, and I feel that's partially what made his mind snap. He flings Krauser's Kaiser Wave like nothing, but, the fact that he had to settle for one of Geese's normal moves instead of the big finisher speaks volumes to me. His inability to do the Raging Storm is an acknowledgement that Geese is better than him and he had to overcompensate with a nuclear-armed aircraft carrier, a pet leopard, and turning Guile into a statue to sleep at night.