Turnout was an important factor. Some Democratic constituencies did not turn out for Hillary Clinton the way they did for Barack Obama. Underlying turnout are the reasons Trump beat Clinton:
For starters, Americans often tire of a single party in the White House after over 8 or 12 years. Americans generally elect the antithesis of the previous president. Barack Obama was the first African American elected president and constantly referenced African Americans and identity politics during his administration. Trump is white and blonde, and he wallows in anti-identity politics. Obama was a Democrat; Trump ran as a Republican. Obama was a committed liberal; Trump is hard to categorize. Obama was invariably polite; Trump deals out insults from time to time.
Many believe Hillary Clinton is dishonest and corrupt, beholden to Wall Street, physically ill, disingenuous, elitist, fake and less concerned with national security than her political prospects. There were persistent stories and rumors that Hillary Clinton was rude and condescending towards her security details, much as she acted after the 2016 election. The Clinton Foundation was viewed by some as a bribery vehicle. Clinton’s physical condition did not likely allow her to visit Wisconsin at all and Michigan as much as she should have. HRC was overconfident and arrogant going into the election. She did not take her husband’s advice.
The political parties had ignored the immigration problem for many years, with the Republicans accepting the cheap labor of illegal immigrants and the Democrats looking for votes. Trump finally and emphatically took a stand on this.
The American people were wary of allowing Syrian refugees to enter the United States without proper vetting, because they are afraid those refugees or their children might turn into terrorists.
The American people were tired of the Bushes and the Clintons and did not want Bill Clinton back in the White House.
The election of Donald Trump assures conservatives that the United States Supreme Court will increase the number of conservative justices or at least not nominate more liberal justices.
Trump was a businessman, not a professional politician, and the country was sick of politicians and the entire Washington political system of which Hillary Clinton was a perfect example. Many voters enjoyed hearing Trump insult politicians.
Many Americans recognized the bias of the mainstream media and sought to oppose it. Most of the political pundits were wrong in their predictions.
Trump defied political correctness and the rigid ideology of previous presidents, both liberal and conservative.
Trump was flexible in terms of his approach and was known as a negotiator.
The lower middle class white person felt disadvantaged by globalization, the loss of manufacturing jobs, stagnant wages, constant demands by minorities, and poor financial prospects. Trump promised to change this.
Trump promised to self-finance his campaign and ended up spending markedly less than his opponent. He came across as someone who is not beholden to special interests or Wall Street.
Trump supported the right to keep and bear arms, which Hillary Clinton attacked.
Trump is pro-life compared to Hillary Clinton.
Trump was well known by virtue of his years on television.
Trump was seen as strong, and Americans were looking for a strong leader.
Clinton bad-mouthed with little policy discussion.