I wonder at the beginning when people form a country, how do they choose their first ever king or queen? How is a monarchy formed?
A monarchy is often formed during a time of war, when a successful and popular general is crowned king.
In the Bible, for instance, King Saul was anointed by the prophet Samuel as King of Israel, but his "dynasty" lasted only one generation because Saul was not successful in war.
But his successor, David, started as a private soldier in Saul's army, quickly rose to captain, eventually formed his own army, defeated the Philistines and other enemies, and became king. His dynasty lasted in some way shape or form for several hundred years.
Rome started out as a Republic, but was eventually embroiled in a number of foreign wars and some civil wars. Its most successful general, Julius Caesar, "crossed the Rubicon" with his army and became king of Rome.
Monarchy happens when people believe in the right of kings (and queens).
Consider how most monarchies developed.
- There was an area with several tribes. Many had chieftains, and that might have been a hereditary office. At the very least, a child of the previous chieftain had better chances to get the job than a random peasant.
- One of those tribes became more powerful, and that tribal leader was elevated above the other chieftains. He or she got a different title and the others took an oath of fealty.
- For a long time, the approval of the Pope helped to confirm legitimacy.
Then a lot of history happened. Some monarchies disappeared again, others prospered. Ursurpers stole the throne but did not question the monarchy, revolutionaries overthrew the monarchy, counterrevolutionaries restored it.
Of course that raises the question where chieftains came from. Same principle, in a smaller area ...