Explanation: Many of the conservative Senators of the Roman Republic who were loudest in condemning Caesar as an aspiring tyrant had very... interesting careers. Namely, many of them supported the coup and civil war of the dictator Sulla a generation before. The difference? Caesar was aligned with the reformist faction of the period (populares), while Sulla was an archreactionary who aligned with the conservatives (optimates), Sulla even going so far as to rework the Roman constitution (already very favorable towards the rich and powerful) to strip the people of what little power they did have.
One might suspect of those Senators that tyranny was not their real concern.
Important note: while I am something of a Caesar simp, and I do believe his populare orientation was genuine, this is very different from thinking of him as a champion of democracy. At best he was an advocate for the prior system of balance between the People's Assemblies and Senate (ideally with he himself playing 'kingmaker' at every election with his massive political influence); at worst, he was only seeking autocracy instead of oligarchy.