Democracy was corrupted immediately , as it always is, doesn't even last a day, not by capitalism, but by government, with the help of the media or as they like to call it 'Public Relations'.
for clarification, you wrote: "Democracy fails when capitalism gets control over the government."
but it should read: "Democracy fails when there is a government." which consequently means it always fails.
in your second sentence your wrote: "Capitalism fails when it runs out of resources and companies can no longer maintain a 2.5% growth rate to attract investors."
but it should read: "Capitalism fails when government interferes with it, which it always eventually will to varying degrees, completely gives up on it, and creates state capitlism, welfare capitlism, communism, socialism, etc...."
so that is the bitter truth, we are a bunch of failures, we all start hallucinating that government can make our lives better in denial of this bitter truth, understandably out of optimism, mixed in with some threats of violence against something or someone, with this optimism we want to find an answer, a solution to our problems, government tells us they can give it to us , so we allow them to violate simple moral principles and grant them authority, we fall into the trap of believe that we can change nature and that the social contract is a just thing.