Explanation: In the immediate aftermath of Caesar's assassination, the assassins discovered that they were actually quite disliked, as a bunch of aristocratic oligarchs who'd just killed the still-quite-liked Populare politician and dictator Gaius Julius Caesar. While Caesar had made several unpopular decisions shortly before his assassination, the grieving Roman mob made it quite clear that they did NOT view his assassination as a liberation. The fact that many of the assassins had previously been pardoned BY Caesar unconditionally did not help their claims of virtue, reciprocity and gratitude being highly valued in the Classical world. Thus, they made an agreement with Caesar's loyalists to avoid an immediate crisis - in which they would receive amnesty in exchange for not rolling back any of Caesar's appointments or populist reforms.
Unfortunately for them, Caesar's loyalists were nowhere near as forgiving as he was. The fact that two of the most prominent Caesarian loyalists after his death were his nephew and adopted son, and his right hand man who had served with him for over a decade did not help the assassins' case. The Caesarian loyalists, the Second Triumvirate (rule of three) had no intention of upholding the amnesty for any longer than the bare minimum to reorganize and rally their forces to start a new civil war against the assassins, and 'proscribing', or essentially condemning them to death and their property to forfeiture, any of those who were dumb enough to remain in the Second Triumvirate's grasp.