Generally speaking, monarchy was either transferred on the death of a monarch to one of their offspring - generally the eldest male, or to the person who killed the monarch (in battle or otherwise) and who then assumed power as the 'strongest' in the land - i.e. the person with the best army!
Your question could raise a lot of controversy, but here is one answer. What people gain by having a absolute ruler depends solely upon the character of the ruler. Some could be benign, others tyrants. Generally there is peace and even some prosperity under a sole ruler. In today's world, we tend to think that the ideal form of government is some type of democracy. However it has been proven several times over that certain countries simply are not ready for the democratic process and in order to stop civil unrest, they need a "strongman".
They wanted to gain power since they asked the pope for help
Through divine right, or in other words the people believed god chose people to become their kings. Strong personality and successful battles increased their power.
To overcome; to gain the victory or superiority; to gain the advantage; to have the upper hand, or the mastery; to succeed; -- sometimes with over or against., To be in force; to have effect, power, or influence; to be predominant; to have currency or prevalence; to obtain; as, the practice prevails this day., To persuade or induce; -- with on, upon, or with; as, I prevailedon him to wait.
Absolute monarchs were not needed. It simply happened. When Charles I became an absolute monarch, he lost his head. When James II of England became an absolute monarch, he escaped England with his life. No one was willing to fight on his behalf. Kings simply try to gain more power for themselves just as presidents do.
Absolute monarchs might hope to increase their power and prestige by expanding their countries' territory. By acquiring more land, resources, and subjects, they can strengthen their control over their realm and enhance their military and economic might. Additionally, territorial expansion can help solidify their dynastic legacy and ensure the longevity of their rule.
Land enables a monarch to have a bigger population, and more people to fight for his army―it enables them to be more powerful, which can be useful if attacked by other neighboring countries.
they get elected(not)
In most cases the death of the incumbent.
After Magna Carta English Kings no longer had absolute power
by birth right
The absolute power gain is the output power divided by the input power, in this case 20 / 0.1 or 200. In decibels this is 10 log 200 which is 23 dBs.
The monarchs can gain salary from his/her job position. For example: he/she should serve people for contributing his/her ability to reach the satisfying result.
The kings of Prussia ruled as an absolute monarchy from 1701-1740. A strong army helped the rulers gain power.
The Saudi kings are absolute monarchs with the power of life and death over their subject populations. Who knows how much of the money from oil they keep for themselves. It's obviously plenty since they all have luxurious palaces, big yachts, private jets, herds of servants, all the bells and whistles of tyrants.
They Sapported Explorations Beacause They Wanted Goods.