The Senators were not elected — therefore there was no Roman Republic to overthrow. The “Roman Republic” was just a fascist oligarchy. Caesar was viewed as a threat to the corrupt senators’ financial interests, and that’s all that was going on.
Caesar was a threat to the Senates financial interests, just as the Senate was a threat to Caesar’s financial interests. Calling either of them corrupt would be accurate, referring to only one party as corrupt would be revisionist.
My sympathy is for a Representative form of government. The Senate was far more Representative than Caesar. The precedent that Caesar set led to Czars, Kaisers and Kings claiming absolute one man rule for the next thousand years. Good thing our founders were more inspired by the ideals of a Republic than those of a Tyrant.
So to be a Senator one had to win at least one elected office (Questor at least), and be appointed by another elected official (a Consul).