Are crowns exclusive to monarchies?
Even after most nations became republics and democracies, why did the elected leaders stop wearing crowns?
As you are waiting I can recommend some earlier answers for you. According to this thread by u/TywinDeVillena and this one by u/sunagainstgold, crowns are and have been a symbol of monarchy, and were even in the Middle Ages mostly worn on special occasions. You might also be interested in this discussion by u/Ainoxos and u/xeimevta, among others