A very simplified version of Austrian economics boom and bust cycles would be that central banks provides money too cheaply which leads to non productive investments resulting in a first a boom and then a bust when those investments don't pan out. Worth noting is that empirical evidence for this is slim at best. I think a better explanation for the 2008 crisis is that commercial banks mismanaged risk of mortgage backed securities. And I have a hard time seeing the current crisis having anything to do with cheap money