Crowd-sourcing for a design is nothing new. It's done for all sorts of things. Typically those things have nothing to do with the military though. It often takes years and years simply to get a design approved by the military and then takes more years to get a functional prototype and it can take a decade or more before a fully functional prototype is in the field and production version rolls off the line. DARPA wanted to find a new military ground vehicle and decided to test a new method to get it.