All the constitutional monarchies started as just monarchies.

Nope.

Spain, for instance, started as a dictatorship.

Then the bastard died of being an old piece of shit, hopefully extremely painfully, and the corrupt fratricidal parasite he’d named as a successor, a descendant of some dude who had been king long before the dictatorship (which started as a coup against a democratic republican government) he’d been grooming for years, was named king.

There was a sham “democratic transition” that defecated a “democratic construction” with the military threatening the elected politicians to make sure the new constitution wasn’t too democratic, and a referendum where the people voted for that thing because at least it wasn’t as bad as going back to the dictatorship.

Then a few years later the parasite (secretly) staged a coup, and then publicly diplomatically dismantled it, enshrining himself as a saviour of democracy and making sure the citizenship wouldn’t push for radical change, lest the next coup succeed.

As the bastard Franco said before he died, he left everything “tied up and well tied up”.