It's not a risk that the economy collapses, it's a risk that his app isn't the #1 search result for Spanish language bible in the App Store. Given the nature of App Stores, he's one Apple search algorithm change away from making $0/month. Someone else could launch a free app that provides the same content and features and make his paid app irrelevant. Five years worth of revenue is a lot compared to that risk.

He also launched an Android version and it didn't blow up like the iOS version.