Couple points. How is it that Usually, you don't see a group of muslims opting to pray in the aisle of a plane. Having said that, Why this group, Why now? Clearly to disrupt. If this was a normal occurance it wouldn't be an issue, it isn't normal or typical. Whether it was to proceed an attack or prove a point, it Was intended to disrupt. You can't do that in an enclosed space such as a plane without things going badly.
These people have also been placed on a no fly list. Again, not typical, or usual, there are many cases where people are questioned and things move on after that.
There is more to this.