I think about giving my best friend, Andy, ultimate power over the country - I'm pretty sure he wouldn't become a brutal dictator. He might not always make brilliant decisions, but I'm pretty sure he wouldn't ignore the experts around him and drive the UK into mass famine, horrific levels of crime, and a climate of fear.
It's thinking about this, or even giving almost anybody I know the reigns of rule, that I don't believe horrible dictators like Mao or Maduro started as good people. I'm pretty sure they must have been power-hungry ab initio.
This makes sense - people who will end up in those positions will be those who seek it. Usually at the expense of everything else because they lust for power so intensely. How do they get there? Probably because most humans can't imagine that monomaniacal obsession with an absolute rule, we fail to detect it in individuals climbing the ladder to the top.
As citizens, we'd be better served by understanding politicians' power-hungry disposition and expecting them to signal they don't have it. That would involve respecting individual freedom, allowing open dissent, conceiving fewer actions as crimes, and limiting the government's power.