Not sure why it was such a surprise
All the major networks were covering it, and President Trump's rallies while he wasn't even in politics yet numbered in the tens of thousands everywhere he went, whereas Hillary Clinton didn't see half of those numbers and there was no enthusiasm for her like there was for Trump.
You could tell that people were excited and engaged for a new candidate, someone who wasn't part of the Washington DC establishment, and someone who promised the creation of jobs, a secure border, and the destruction of ISIS.
Most people forget that President Trump got into office mostly because of the 8 abysmal years of Obama. Had Obama succeeded at prospering the American people during his tenure, you would not have had a Trump victory in 2016.