Many people were surprised that the polls, which are usually good at predicting the outcome of presidential elections, were so wrong this time. But let’s put things in perspective.
The polls accurately predicted Clinton would win the popular vote. But suppose the Comey letter caused a small, barely detectable shift in votes in the close battleground states.
That definitely could have shifted the electoral college vote to Donald Trump. And that is the most logical explanation of how Trump got “elected” when the polls predicted otherwise.