Because all the connections between ideas within a domain have already been mined for everything worthwhile. By connecting two domains, you're exposing a whole

Because all the connections between ideas within a domain have already been mined for everything worthwhile. By connecting two domains, you're exposing a whole new set of connections between things that are rarely connected. There's a theory / definition of creativity that says that it's simply the ability to connect seemingly unrelated things. This is an example of that.