It wasn't that by the end they didn't understand the problem, but rather that by just attacking "build a human powered plane that can do <x>" they were not making progress. Realizing that in order to "make a human powered plane that can do <x>" they needed a lot more data and their development method wasn't getting them that, they changed to "make a human power plane in such a way that I can get a lot more data quickly". I'd assert that realizing that the problem is getting data too slow as opposed to "working" too slow is not one that's immediately apparent to most humans.