There's another, remarkably simple reason why Islamic terrorist attacks are less likely to be referred to as lone wolf attacks: because they're not. See https://www.nytimes.com/2017/02/04/world/asia/isis-messaging... They're pretty much all centrally co-ordinated, even the ones that were initially assumed not to be, including the smaller-scale ones that just target a handful of people at a single bar or involve someone going on an axe rampage on a train.