As people become more segmented, isolated, or stripped of a sense of belonging to or a connection to the people around them - then the frequency of aberrant events may increase.
Definitions for terrorism drift and change over time, not for the least because states employ methods that are terrorism in the objective case. Within the past century the Prime Ministers and Parliamentarians of many countries have been in the past "terrorists".
It often seems to come down to who's writing or rewriting the accounts - and all of it no comfort to the person who was just killed, or their families.