According to Bruce Bueno de Mesquita in The Dictator's Handbook, Caesar's murder was (obviously politically motivated) due to him helping the people at the expense of many of his backers or Rome's most influential people. Caesar helped the poor citizens, such as by providing land grants to former soldiers, getting rid of tax farming, and relieving the people's debt burden by 25%. This came at the expense of Rome's prominent citizens, such as those who were owed money or were large landowners (i.e. tax farmers or wanted to buy more land). These people were well-represented in the Roman Senate and killed him.