The reason government is corrupt is because those that serve are the least worthy, since they seek out the power and the most worthy do not. The majority of any sufficiently old government will be those who seek to abuse the power to elevate themselves. They work with other people like themselves in other organizations to take wealth and power from others. The only stay against such corruption is to prevent the government from acquiring those powers and to find a way to sift out the unworthy while elevating the worthy into power, and removing them from power before they are given the chance to go bad.