Institutions exist because people believe in them.
Take for example the Supreme Court of the United States of America. Why does this institution have power to do anything? It’s just 9 people sitting in a room. Why should what they say matter to anyone? It matters because hundreds of millions of people believe in that institution. We believe that some rules written on a piece of paper matter, and we are all going to follow those rules.
Yes, you might say, but we don’t have any choice. That’s kind of true. When the believers count in the hundreds of millions, one person can’t really resist it. Regardless of what you think, if everyone else believes that everyone else believes, they are going to follow the rules and bring significant consequences on you if you deviate. Thus, institutions take on a life of their own. They can include mechanisms for reinforcing their own continued existence. This the case for nation states, churches, and so on.
Someone becomes president in the US because we all acknowledge him (so far no her) as the winner of an election. It is our belief, our choice, that brings the office of president into existence. And we can just as easily destroy the office by choosing not to believe. This is why Trump’s behavior is so dangerous. He is attacking the very foundation of our constitutional democracy by sowing doubt about elections and the legitimate transfer of power. Remember, nothing sustains it other than our mutual belief.
As a side note, Money and Wealth are also institutions relevant to our national discussion. Money is only any good if it influences people to do things, like fix your car or grow food a thousand miles away and deliver it to your door. Wealth is a claim to ownership. It says “I have the sole right to benefit from the use of this thing (factory, land, organization, whatever).” But that only has force if everyone accepts the idea, such as those working in the factory or packing boxes in a giant Amazon warehouse. Wealth, in a capitalist system, means you benefit from the labor of others.
Slavery is an institution. If slaves outnumber their masters, why would they go along with it? This has always been a mystery to me, but I think it has something to do with setting up the rewards and punishments so there is a high barrier to leaving. That structure is largely enforced by the slaves themselves. Why would slaves work so hard to sustain a system in which they are clearly the losers? It boils down to belief, and masters are good at telling a story that puts them on top.