I am not very familiar with the right-wing scene, but something like "martyrdom in the fight against the traitors of the state" doesn't sound too outlandish to me, at least for the really extremist individuals. Parts of the right follow the idea that the current government is destroying Germany, and that rhetoric has become more mainstream - manifested in the term "Lügenpresse" ("lying press") and similiar diffamations. So singular radicalization seems quite possible. Either way, considering the situation the death toll seems relatively low. I'd assume if it had been tightly coordinated, the whole thing could have ended up a lot worse (e.g. blowing up trains in the metro).