Eh, Islam itself is the carrier for ISiS and offers a wide network of sympathizers who may or may not be able to openly support terrorist goals, but re-packaged as 'normative Islam'. 'White supremacists' are truly exiled from 'normies' in the West because their ideology is not 'cool'; far-right terrorists are not going to have a stock of replacement soldiers from either Christian or secular populations in the West -in the same way incel Muslims are tapped for replenishment of ISiS ranks.