There are a lot of different people in the world. Some of them crave structure at the expense of anything else. Some crave symbolism at the expense of everything else. If a despot or coup leader writes a constitution, those people will get on side for free. It costs nothing to have a constitution.

And I doubt either of us have done a survey of dictators; a lot of them probably do just ignore the local constitution.

It is important to remember that people who think we should follow the intent of a 100 year old law (or even a 10 year old law) are a tiny minority group. The majority of humans are here-and-now, what-looks-like-a-good-idea-today?, what-do-I-see-in-front-of-me people.

Sometimes despots write new constitution and then ignore it completely too

https://en.wikipedia.org/wiki/1936_Constitution_of_the_Sovie...

Sure they write new ones to justify their rule. I’m thinking of constitutions in working democratic countries who protect the rights of citizens and how they only provide rights as long as institutions are there to provide a a theoretically just enforcement. After all constitutions in most western countries came about to restrain the sovereign.

What's the difference between the US and a despotic regime? We have a gulag system. There is a degree of legal nihilism that borders on lawlessness. For example, the DOJ charged someone with a federal crime for throwing an imported tequila bottle. When the laws mean anything and nothing, you have rule by fiat. There's corruption everywhere...