Well, the business strategy for a bank isn't really rocket science. Right now they focus on grabbing market share, which isn't too hard in countries like Germany. They've also introduced a few products (savings, investment, insurance) as a broker, which allows them to gauge the demand among their customer base and develop popular products in-house in the future.

While I don't expect them to sell mortgages anytime soon, they have many other ways to make profits. And if they manage to keep their footprint low compared to the way big traditional banks are moving online, I'm sure they'll be fine.

Or they could end up being acquired. (I hope they're big enough not to, but consolidation is a real issue in retail banking).