I have been working on a theory. It's a corollary to Parkinson's Law, which is "work expands so as to fill the time available for its completion."

My new version is: "Complexity expands to use all the brainpower available." Interestingly, the reason "moonshots" work is that it makes the basic problem you're working on so fundamentally difficult that you don't have as much room to wastefully expand the complexity of your solution.