Why did republics go out of fashion or how did monarchies make

>>1560161
Monarchies naturally emerged from the barbarian chiefdoms.
The Italian peninsula was more used to urban life and civilization so republics and other classic forms of government flourished.

monarchies are generally produced from less advanced societies (PRODUCED. they don't necessarily have to move on, but that is where they come from) because it is less complicated and more efficient (especially in war) than a complicated democracy/republic. hence why rome had consuls and wartime dictators.

>>1560161
I feel like Christianity would have something to do with. Stuff like Charlemagne and other European kings being blessed by the pope. A single monarch could probably act out gods will better then a group of people who have checks and balances against each other.