They almost never 'take' power. Politicians are given power and you can see many historical examples of this. Many of the worst examples have simply abused power that never should have been given to government by the people in the first place. It was always going to happen and doesn't just pop into existence out of thin air.

That isn't to say that there aren't individuals within these contexts who didn't consent, only that enough of the culture and population did. Otherwise, it never would happen. Hitler wouldn't happen. Mao wouldn't happen. Stalin wouldn't happen. People like that were given too much power because of bad dominant culture/philosophy and abused it.