In reality, predicting a...

In reality, predicting a Clinton win was valid if one simply looked at the latest within-state opinion surveys. It was never a sure thing, but it was statistically significant. That means Clinton would lose, by random chance, only one time in 20, but sometimes, random chance happens.
80,000 votes in four states out of 127,000,000 cast nationally is 00.06%. There will never again be a contest for president between Trump and Clinton. There are no lessons to be learned.