It's an alignment problem. Any ruler has to keep the right people happy to stay in power. An autocracy has a couple choices how to do that. You can use military

It's an alignment problem. Any ruler has to keep the right people happy to stay in power. An autocracy has a couple choices how to do that. You can use military and police, you can use religion, you can make the population richer with great economy or great social programs, you can bring law and order to a previously crime-torn country, etc. Each of these gives someone the power to dethrone you, and the state typically has to spend large amounts of resources to keep those people happy. The "genius" of democracy is that it guarantees that at least half the population is in that group, because a popular vote can dethrone the government. That doesn't mean they are the only group the government is paying off to stay in power, but better to be in than to be out. One of the problems we have currently is that the population is aging, meaning it's more rational to cater to old people who on average dislike change. This eventually leads to stagnation or even regression.