Such as? There's seizing power and holding on to power, I don't see magic PCs have access to giving wizards that much of benefit.
Let's take Bob, common every day dude, and Steve, the sorcerer. They both want to rule over their city, which was just founded.
Someone wants to stab the ruler, kill them, and take over.
Bob is a normal dude. He is very stabbable.
Steve can be wearing invisible armor all the time and summon a shield of force to protect him. Steve is not very stabbable.
Bob wants to have a guard force that protects his city and people, as well as himself. So he hires a bunch of people.
Steve wants to have a guard force that protects his city and people, as well as himself. So he hires a bunch of people. He can also at anytime summon additional forces beyond that, for emergencies.
Bob needs to sign an agreement with another kingdom, that may decide the fate of his people. He has nothing but his wits and advisors to decide on the best course of action.
Steve needs to sign an agreement with another kingdom, that may decide the fate of his people. He has nothing but his wits, advisors, and the ability to cast divination magic to peer into the future and know the general results of his actions to decide on the best course of action.
Dealing with poison? Magic gives you more options
Spycraft to send coded messages? Magic gives you more options.
Communication, construction, protection from diseases? Magic gives you more options
This isn't a question of "what specific ability gives the Wizard the ability to rule a nation" this is a question of "since spellcasters always innately have more options than mundane people, why aren't they in charge, since over time those additional options would have prevented them from being removed from power and kept their nations prosperous"