The given reason that's been floating around is that he got death threats from Muslims. This is a little odd for a number of reasons. He should revel in the deaththreats. If somebody tells you to stop fighting for Jesus or they are going to give you an express pass to Heaven, then clearly the plan for a true believer is to go run and hide? WTF. That doesn't make any sense.
Some others suggest that it's because he was scamming money. That was the first respectable thing the kid seemed to do. Start scamming cash off his rube followers. The venomfangxsite says that
"This site has been taken offline by the parents of VenomFangX, they don't support/share his views and apologize if he has offended anyone. This site will be offline for good in 3 days."
Others speculate that his parents got angry at the money scamming or because one of VenomFangX's followers killed himself and a girl.
In any event, it doesn't look at all like Muslim deaththreats did it, nor really should they have been able to.