Governments are not especially the form of political arrangements they practice, they are what the people expect from them. Political arrangements are machines operated with people as parts. For the machine to function, the people have to play their part.
Plato described three basic expectations people have from their government.
First, that it would not express any particular idea of what would be a good government. Second, that one group knew what they wanted from the government and they were getting it. Usually that would be money, but it might also be honor, or fighting for honor. Honor is making a show of what your group will do to keep control of the government. Third, is a government that expresses one idea of how life should be lived.
Elections, military takeovers, riots, protests: the actual mechanisms used to form the three types of government are unimportant.
Democracy has one clear advantage: the government knows that killing people is not what people expect, not what people expect from people. Everyone can agree on not wanting to be killed. What they expect from the actual administrators of the government is that they will kill when it's in their personal interest, like all government officials do. When the government kills too many people, people understand that the government is not what they expect. They then might cause it to fall.
A people that expects the government to be of people who seek money or honor or shows of victory, or seek to make life for them on one set pattern, can expect the government to kill them.
Democracy is a matter of expectations. Democracy is the form of government in which its people have the least expectation of being killed. A people that makes money or honor or victory its ideal, has to expect many of themselves to be killed by their government in the service of those ideals.
When we say our country is no longer a democracy but a government of the wealthy, we are not talking about money, or corruptions of electoral mechanisms. We are talking about danger of death by government.
FURTHER READING How Expectations Of Democracy Are Forgotten:
1. From Democracy To Totalitarianism
2. The Mathematics Of Stupidty
