I have not seen all the details, but all the other crimes seem to be those of planning. Are they being charged for thinking violent thoughts while carrying a gun? Teaching and planning (even if they are about violence) are not violent in and of themselves to justify that charge. That is, unless there is more that I have not heard. Did they sink a South Korean patrol boat?
I’m not one to trust anything that comes out of the government, but if these guys were planning something like this and the government found out about it, it’s hardly reasonable to expect them to wait until after blood had been spilled.