The evidence shows the opposite. Political leaders (in any system) want to act in the short term. Democracies simply constrain them.
No “lifetime leaders” are guaranteed a life term. They must continuously fight for political survival. (And with that, often, actual survival.) Dictatorships deploy, with limited constraint, their immortal nation’s power on mortal time scales.
(Democracies’ rotation of leaders also allows for fixing mistakes. Dictators are constrained in terms of backing away from bad decisions. They thus have a bad habit of doubling down on stupid decisions.)