At the same time, if the monarch (in a system like that of Britain) actually started using and abusing their theoretical powers, they'd quickly have the whole of the country turn against them. And they have a lot to lose if that happens!
In a presidential system, the President is both the theoretical and actual head of state. They're already in the top spot, and the only thing preventing them from staying there is convention or laws which are subject to change, and enforcement of which is largely under the President's control.
A more ceremonial President might work as well, but the thing is, an elected head of state has less to lose by abusing his powers, and far more to lose by properly following convention and thus stepping down.
https://theconversation.com/the-queens-gambit-new-evidence-s... https://www.telegraph.co.uk/politics/2018/05/09/could-army-c...
But don't worry, as long as people live in a fantasy world where they believe they are just ceremonial figureheads and a benign presence, their position at the top will never be challenged. And at any moment when it does, peoples emotions/grief will be exploited to maintain the institutions by using north korea style propaganda campaigns and security operations:
https://www.theguardian.com/uk-news/2017/mar/16/what-happens... https://www.theguardian.com/uk-news/2021/sep/03/security-ope...
Between the two...could you really picture Queen Elizabeth attempting to seize total control of the state--much less accomplishing it? Or the monarchs of Norway, Sweden, Denmark, Spain, Belgium, the Netherlands, or Japan?
I can picture a President attempting to seize power in a Republican system. In fact I can point to several specific examples from the past few decades, successful or otherwise.
I'm definitely not saying constitutional monarchy is the perfect system, at all. I'm just saying that after spending most of my life with the assumption that monarchies were just a quaint anachronism left over from days gone by, a sort of political appendix...I've started to notice that they seem to have interesting properties and robustness that other systems might lack. It's possible that the monarchy serves a useful purpose after all (actually...much like the appendix).