Except of the social networks I browse, stephenking.com is not one of them. So really no I wouldn't hear of him. I'm sure his die hard fans will though.
I guess if you never step foot into a library, bookstore, movie theatre, etc. Sure.
King does not sell books because of his presence on a social network. He sold 350 million copies of his books before Twitter was even invented.
"die hard fans" the only ones to hear of King? Big lol.
He’s highly culturally relevant, but not because of anything he’s done lately.