Both Cassius and Brutus did not want Caesar to become the new Ruler, but both had different reasons. Cassius didn't want Caesar to become the ruler because he would rather have been Ruler himself. Cassius was also very jealous and envious of Caesar, so he had no problem killing Caesar. Brutus joined the conspiracy because he didn't want Caesar to become the ruler because he believed that Caesar would become a dictator and the people of Rome will suffer. Brutus loved Caesar, he could not make up his mind on whether to go to the conspirator's side or stay with Caesar, but he came to the realization that he loved the Roman Republic more. Hence the quotes "Not that I loved Caesar less, but that I loved Rome more.", and at the end someone says about,"This was the noblest Roman of them all" because only Brutus's intentions were not corrupt.
Cassius and Brutus were both military strategists. Brutus was not a very good military strategist because he made many mistakes in choosing his move