This happens when a leader acts with brutality that exceeds threats posed by opponents.
It is not uncommon for opponents of a government to take measures that are outside the ambit of the law to put pressure on it to meet a particular demand or take measures to overthrow it. Examples of heads of state pardoning people who have used violence to try to overthrow them and even going further to integrate them in the management of public affairs do exist. People who have engaged in combat against each other resulting in the loss of many lives have also been known to come around the table to negotiate to form coalition governments.
Hence being in or out of office is just a matter of historical chance. One person out of millions must become a head of state. Hence anybody who occupies this post should be very humble and magnanimous. On the other hand, if the person assumes the office as a personal property one must become intolerant of dissent and would do everything to liquidate it. Hence any act which poses as a threat would be mercilessly dealt with, with the hope of teaching others a lesson. This is what is meant when one says the lion has tasted blood.
Unfortunately such measures never bring peace and stability. They only incite a greater spirit of revenge. The road to peace is to have humble and tolerant leaders who are ready to settle disputes in good faith in the public interest.