Why were the Senators angry at Julius Caesar?

Most of the conspirators were senators, and many of them were angry about the fact that he had deprived the senate of much of its power and prestige. They were also angry that, while they had received few honors, Caesar had been given many honors.

Caesar's assassination and the Second Triumvirate

Explanation:

Most of the conspirators were senators, and many of them were angry about the fact that he had deprived the senate of much of its power and prestige. They were also angry that, Caesar had been given many of the honors.