We think we're quite sure in our observations, so that helps, but to be able to claim how the simple laws can exactly produce what we see, we have to do a lot of work. Just like what Newton figured out was not provable before without all the computations:
My "feeling" is, it's not "intuitive enough" to "guess" any answer without a lot of computing:
https://www.quantamagazine.org/coder-physicists-are-simulati...
We think we're quite sure in our observations, so that helps, but to be able to claim how the simple laws can exactly produce what we see, we have to do a lot of work. Just like what Newton figured out was not provable before without all the computations:
http://www4.ncsu.edu/~kimler/hi322/halleytale.html