The biggest cause of regime change seems to be the succession of power and the fears around change occurring during succession of power. A ruler dying through old age is a common source of regime change in history as people with varying interests start vying for that position and ensuring the new ruler holds their same interests.
It's the exception rather than the norm. Rulers are typically just replaced by their successors.
I mean, I gave you multiple examples of some of the most powerful people that ever lived, none of which fall into this category you call the 'norm'. You just completely ignored that and continued with your baseless fantasy.
Upon his death, Genghis Khan was succeeded by his son. Mao was succeeded by Hua Guofeng, vice chairman of the CCP. Stalin was succeeded by Nikita Khrushchev, First Secretary of the Communist Party of the Soviet Union.
And the power was less centralized after each of these deaths.