There is a problem in the perception of terrorism. Most terrorism isn't islamic (at least in the West). But you wouldn't know that from the media.
But it's easy to see where that perception comes from. If you look at those numbers from Europol, you will notice that
most casualties from terrorism in Europe are caused by islamists.
Most attacks by far are carried out by separatists, but these tend to be very localized and usually don't target civilians. These attacks are in fact perceived as very threatening in Spain, France and Northern Ireland, but less so outside these regions.
The most talked about terrorism case in Germany is the NSU group, but they acted more like serial killers, didn't seek publicity and were only discovered by accident, years after the murders. So they are now perceived as terrorists, but there was never a scare of right-wing terrorism during the time they were active.
Breivik was a lone wolf, while most islamist have or claim to have some connection to a greater network. This is I guess the main problem, every other month you hear of a foiled attack by a salafist network. Even if a lot of these people are probably relatively isolated, it
appears as if there were some mayor organisation behind all this. This perception plays into the hands of the terrorists, as they seem much more dangerous than they actually are, but it also makes it more difficult for non-muslims to distinguish between conservative muslims and potential terrorists. The whole "all muslims are terrorists" idea seems more of an US-thing to me, if you live in a medium-sized german city, you will probably see lots of muslims everyday without fearing for anything all the time.