This question gets to the heart of the play. In my opinion, the tragic hero in the play is Brutus and not Caesar. What makes Brutus the tragic hero is that he is torn between duty to state and personal desire.
From a personal point of view, Brutus loved Caesar. For instance, from a historical point of view, Caesar pardoned Brutus when he was on the losing side of civil conflict. Moreover, Brutus respected Caesar. In short, there was true friendship.
On the other hand, Brutus was also bound by duty to defend the Republic. This was a real concern for Brutus as his family was rooted in the Republic. In fact, his great ancestor was one of the founders of the Republic.
Based on these two points, there was internal conflict. Should Brutus honor Caesar or the Republic? Should Brutus follow his heart for Caesar or do what he thinks is best for Rome.
Shakespeare does not give us an answer. Yes, Brutus was wrong in joining the conspiracy, but he was a honorable man for doing so based on his convictions. In view of this, there is no great answer. People will differ. But this is why the play is so enduring.