Why did Viktor Korchnoi leave the USSR? Why did Viktor Korchnoi/Kortchnoi leave the USSR?

Maybe the answer could include a little more trivia since he is such an interesting character.
The short story is that the Soviet chess authorities at the time were blocking Korchnoi's progress and severely limiting his opportunities to play, as Karpov had been selected as their favorite son. It was the same sort of impediment that Kasparov later faced when he was on his own path toward dethroning Karpov, and it also echoed the scenario from decades before, when it was rumored/suspected that Paul Keres had been forced to take a backseat to Botvinnik.