Even in college-level math education you can encounter the situation where you have a homework problem, and after pondering it for a while there's some simple insight that cracks the problem, but even bringing it up to homework standards, to say nothing of paper-publishing stardards, requires quite a bit more work.
And you may also experience the simple insight that cracks the problem, and in the process of finishing up the work to bring it up to spec you end up invalidating it.
Of course my homework never ran to 81 pages, but I suspect it's just scale.
I can certainly say I've had cases where I was presented with a business problem, and the solution was basically obvious to me in minutes, but manifesting that out in real code took weeks and actually quite a bit more than 81 pages of code. My system didn't disprove decades of conjecture that it was impossible, of course, but I think it's also more a quantitative difference than a qualitative one.
On the one hand, I don't want to disparage the excellent work done by professional mathematicians, but on the other, I do want people to understand these are humans, and I don't want you to just casually assume that you could never do anything similar. It is a delicate balance.