How did Julius Ceasar and Caesar Augustus transform rome?

The two men transitioned Rome from a Republic, which was ruled by the Senate and where the citizens at least had a theoretical say in how the government was run, to an Empire where the Emperor held nearly absolute power(as long as he could maintain the loyalty of the troops). While both men at least pretended that the Senate still had some real power and influence, both in practical terms dictated to the Senators what was going to be done. The ination of Caesar was far too late to turn matters around and save the Republic. Power was aculating among those who could command the legions, and who were willing to use those legions in their own interests.