It makes sense to me why there's such high volume of fraud across such a vide variety of vectors.

If I was going to try and steal an election, I'd go for broke. I'd do it in as many ways possible and to the maximum extent possible. I'd steal enough votes so that even if they managed to invalidate 95% of them, the remaining 5% they weren't able to invalidate would still be enough to put me over the line.

That appears to be what they've done here. They've stolen votes on such a massive scale that it would be impossible to invalidate them all.