User blog comment:Pryamus/Lore: Christian / Satanic symbols in Diablo/@comment-3423357-20140518225621

Probably a combination of two things: First, the series now has its own deep lore to explore and doesn't need real imagery to use as a crutch anymore. Second, making the game less overtly religious will offend fewer people and sell more copies. The second point should not be taken lightly, according to the most recent sales I could find, Diablo I has sold 2.5 million, Diablo II has sold 4 million. They were considered great successes in their time, but if Diablo III had only sold 2.5 million copies up until now, it would probably have been considered a dismal failure. Instead, it broke sales records and has surpassed 12 million, nearly double the other two put together.