History Lesson: Why Trump's Victory Is Not A Surprise

So, most everyone is just so shocked Donald Trump won the presidential election.
Had people knew a little bit history on presidential elections for the past 76 years or so, knew when a president has been in power for 2 terms, the opposite party of the president usually wins the next presidential election.
So, follow along please:
Harry Truman-Democrat president from 1945-53
Dwight Eisenhower-Republican, president from 1953-61
John Kennedy/Lyndon Johnson-Democrat, presidents from 1961- 1969
Richard Nixon/Gerald Ford- Republicans presidents 1969-1977
Jimmy Carter-Democrat president 1977-1981
Ronald Reagan- Republican president 1981-1989
George H.W Bush Republican president 1989-1993
Bill Clinton- Democrat president 1993-2001
George W. Bush- Republican president 2001-2009
Barack Obama- Democrat president 2009-2017
Donald Trump- Republican 2017-?
With the exception of the George H.W. Bush presidency, the party's of the president change basically  every 8 years. (or in the case of Carter, 4 years)
So, history repeated itself again when Trump won the presidential election after 8 years of Obama.
Most smart people should have known this pattern, but then most supposed smart people also thought Hillary was going to win in a landslide.