Why a king and a conscious monarchy is required?
After the battle of Kurukshetra ended, Pandavas went to Bhishma seeking knowledge and blessings. Yuddhisthir asked him, "O grandfather! Please tell me what will happen if there is no king,
Everyone is equal and free to do whatever they want. Is a king even necessary?"
Then Bhishma told him about the necessity of a king in any state. He tells that, it is the duty of any state citizens that they choose a king to represent them.
Without a strong and capable king, the state will become like a forest without a lion. Hundreds of hyenas will start feeding on the animals and they'll destroy the essence and balance of the jungle.
When there is no king in a country, people start looting the resources and harassing women of the poor and weak people. The state is despised where there is no king.
It's said that in the form of a king, citizens choose an Indra for them who takes care of the citizens like his own children and works for their nourishment.
Bhishma says that wise men leave the place where there is no king or even a weak king.
It's also mentioned in Sabha Parv when Brahmin host talks to kunti in the village. He tells the similar thing about the kingdom.
It was due to a weak king that demon Bakasur was dominating the place.
Same happens when you have a weak king or no king.
According to Bhishma, wise citizens even invite a strong and righteous king from another state to tak over a king who is incapable to rule the state.
Because if a king is not ruling as per Dharma, he will destroy his own citizens.
A weak king can't punish the criminals properly and what is the use of a king if he can't even punish them who try to harm the state and it's people.
A weak king is similar to no king.
In case of anarchy, a person becomes happy to loot someone weaker than him. But when another strong one loots him, even he also feels the need of a king.
When there is no king, even barbarians can't live with peace.
A barbarian is looted by duo of them.
The duo can be looted by a group of barbaric people.
Slavery starts to propagate in such state and weak people are pushed into slavery.
Women have to go into most vicious cycle of harassment.
We can even see this in middle East today.
That's why deities made the kings who were righteous.
It's said in the scriptures that a small fish is eaten by a big fish and when all the food is gone, that big fish also dies to hunger.
So people made a rule that whoever in the state would be a tyrant and would torcher people, the state would discard them and throw them out of the state.
But later same people made their alliance and start sacking the state.
Then people went to Brahma and asked him to provide them a strong king.
They would consider him as Indra and worship or regard him as their guardian.
Brahma appointed Manu as their king.
Manu was a righteous man.
He was afraid that being on a powerful position would turn him into a greedy Vulture who would resort to Paapkarma.
Then people made a rule to give tax to the king.
The king in turn will take care of the citizens, protect them and nourish them.
A king would get 1/50 of the cattle, 1/50 of the gold and 1/10 of the grains produced.
He would use them for the citizens. When a king will require, the citizens would help him in every way possible.
Ref: Chapter 67, Anushashan Parv, Shanti Parv, Mahabharata.