The reason it's important is because his motives significantly play into the solution of the problem.
For instance in Canada we had a guy storm the parliament and kill a soldier pledging his act to islamic terrorism. People freaked out thinking it was some coordinated attack and follow up was needed.. But was later discovered the guy was mentally unstable and homeless. Essentially no more follow up was needed. Whereas in Paris you had a live terror cell.
If you can't see the difference between those I don't know what else to say. Very different solutions to dealing with lobe wolf vs terrorist organization