What was the main reason behind the tension that eventually caused the collapse of the Roman Republic?

Answer 1

The main reason behind the tension that caused the eventual collapse of the republic was in a way threefold. There were three groups of senators who had different political outlooks. They were not political parties as we know them, but men who thought alike. There was the so-called populist group, who basically were for change in debt and land reform. They were pitted against the so-called optimates who were the "good men" and opposed change. They wanted things to continue "in the way of the ancestors" or "mas maiorum". Then there was the largest group who were simply out for themselves. They would vote with the populists when it served them but would go over to the other side if it were to their advantage. This political situation not only caused tension in the senate, but it spilled over into the streets at times, such as the ruckus between Milo and Clodius and eventually the war between Caesar and Cato.