Now we're in a relative lull in deaths by terrorism. That seems an absurd statement, but it's the truth, as shown by this chart. What's the difference between the past (i.e. 1970's and 80's) and now?
We forget how active the IRA groups and the unionist opposition were on the killing front. We forget the Palestinian groups were terrorists in the 70's and 80's. We forget the Basque groups. We forget the small leftist/anarchist groups. Put them all together and they caused more death than ISIS and Al-Qaeda.
Perhaps it's just our amnesia. It's not the motivation--murdering because of religion was arguably what the IRA did--were they radical Catholic terrorists? I think not.
More likely it's familiarity--most of the groups had a history and their terrorism was something we were more accustomed to so it somehow seemed less dangerous. And importantly, most of the groups seemed to have a defined target, where today the ISIS terrorists seem to be attacking "Western civilizations".
Bottom line for me: chill and think historically.