People just forgot about its origins, and recycled the names and themes, I suspect. I doubt it has much to do with the original monarchy vs republic debacles, and I also doubt they had any form of coronation, or that any of them have any solid idea of the predecessors.
When I quit the game, it was namely because I was trying to push the monarchy forward with non-mechanical importance and develop it further, precisely become people had already begun to forget about the whole thing. I wanted to codify the monarchic rules and powers and was opposed by people seeing the move as a power grab.
I suspect it's as with Madina, the continent's republic spawner, that is now a monarchy. A very few greedy people presiding over masses of indifferent people with little regards to culture. Someone went "I want to be king", and people just went "meh, okay".