cults very very rarely survive the death of its founder

That’s not true at all.

The USSR lasted a mighty long time after Stalin’s death.
Maduro is still in power in Venezuela long after Chávez’ death.
Cuba is still doing Fidel’s revolution, at least in theory.
The Kim family is still in power long after Kim Il Sung’s death.
The Ayatollahs are still in power long after Khomenei’s death
…