I think they are the awkward person who never speaks up irl. I mean, probably not the purple-haired ones who dress like clowns, but the fat, quiet one in your office or hanging around your friend group. Most people don't care enough about them to actually follow them online, they just sort of tolerate their presence, so most people don't know what a radical nutjob they are. All the people they talk to on social media are ones they only know online.