He was already in command of the legions, and was just without the city.

He had endeavored to buy Cicero, but had failed.

Having failed, he had determined to be rid of him.

Clodius was but his tool, as were Pompey and the two Consuls.

Had Cicero endeavored to support himself by violence in Rome, his contest would, in fact have been with Caesar.
Cicero, before he went, applied for protection personally to Piso the Consul, and to Pompey.