My private theory is that Bond indeed killed the real Blofeld in the pts - who kept making doubles because his first effort was so successful that this Blofeld 1.1 started to believe he really was Ernst Stavro Blofeld and caused all manner of mischief and confusion in the organisation.
After Bond rid him of the only person to challenge his claim, Marty Blimpman from Hoboken (his real name and origin) set out to conquer the world. This also explains why Bond isn’t simply shot at first sight throughout the film - subconsciously Blimpman is grateful to Bond - and why Britain doesn’t feature in his scheme at all: Marty Blimpman’s plans have never been foiled by the UK. 