How did Caesar win his mens loyalty and devotion?

Answer 1

Julius Caesar achieved approval from the senate by being a clever Roman politician. He stacked the senate in his favor using the powers of consul and dictator. He raised capable men to positions in the senate and those men in turn were obligated to him. This was the Roman cultural custom of "amicitia"

which was literally a friendship, but it had deeper undertones and obligations. Don't be misled into thinking that the entire senate was conspiring to assassinate Caesar. It was merely a few-- 30 to 60--depending upon your source, who were in on the conspiracy. The rest of the senate was either loyal to Caesar or neutral.

Answer 2

He promise to keep Rome a republic.