Everybody was predicting a crushing electoral victory for Clinton. Instead she suffered a crushing electoral defeat. Look at 538's own forecasts [1]. You'll note he put the odds of Clinton Winning the popular vote but losing the electoral college at just 10.5% when not only is that what happened, but it happened by a wide margin with Trump's electoral victory margin being even greater than was predicted for Clinton's.
As an aside, even the popular vote aggregates are somewhat disingenuous since they're heavily based on major polling screw ups. For instance Clinton's margin of victory in the popular vote nation wide is smaller than her margin of victory of victory in California alone. 538 was off by more than a million votes there, which they're now using to try to spin into defending the aggregate numbers (which are not even what the election was predicted on to begin with.) This is just really disingenuous stuff.
[1] - https://projects.fivethirtyeight.com/2016-election-forecast/
You also seem to be under the impression that the polls were drastically off in 2016. They weren't: https://fivethirtyeight.com/features/the-polls-are-all-right National polls in 2016 were better than average, and while state polls were worse-than-average it still wasn't the worst error in the last 30 years.
The problem was never really with the polls (though there are problems there, most notably herding). The problem was with the narrative around the election which cited polls as evidence that Clinton was a sure bet even though the polls didn't really say that.
Of course, if you have evidence that the polls were more wrong than this I'd like to hear it.