An army of Terminators can't keep you safe from retaliation. Anyone who tries to take over the world with killer robots will be fought by other people. You might be able to provoke World War III by unleashing killer robots against all the world's governments and their militaries, but you won't be able to prosper or even (probably) survive.

You use the Terminators to pretend to be real people and than vote for other Terminators. You take over every country in the world without anyone noticing it even happened.

> Seriously, if you have that kind of power, what's the incentive to let everyone else live?

Ethics and morals, maybe? Basic human empathy? I think I get where you're going with this. There are those, sociopaths and psychopaths for example, who would go to any length to get that kind of power and... what, when they have their T-3000s they're suddenly gonna have a come-to-Jesus moment? Unlikely, yeah.

Ethics and morals are traits that prevent people from raising to power, which is why people in power tend to be sociopaths.