Why? If you're serious it was the candidates chosen by both parties in 2016. Both choose unwanted candidates by America as a whole and independents especially.

One in Four Americans Dislike Both Presidential Candidates


If you scroll down you see 24% of republicans viewed both major party candidates unfavorable, 20% of Democrats and a very high 54% of independents. Only 4% of Republicans had a favorable view of Clinton, 4% of Democrats saw Trump favorably. Independents, 30% had a favorable view of Clinton, 33% of Trump.

So the election devolved into a decision of who one disliked the least, voting for the candidate one wanted to lose the least, not win, but lose the least. especially among independents as 90% of Republicans and Democrats are going to and did as history has shown, voted for their candidate regardless of who that candidate was.

You actually had only about a third of all Americans wanting Trump to win, a bit over a third wanting Clinton to win, all the rest regardless of their reasons, voted for the candidate they wanted to lose the least. They wanted both to lose. This latter was especially true for independents, the non-affiliated group with either party, the less to non-partisan and definitely less ideological. Call them the middle of the roader's. 12% thought it important enough to go to the polls to vote against both major party candidates, some 9 million voters because they disliked both so much, they were willing to vote for a candidate they knew didn't stand a chance of winning. Disgust rained among independent at the choices made by both major parties.
It's high past time that we start electing Americans to congress and the presidency who put America first instead of their political party. For way too long we have been electing Republicans and Democrats who happen to be Americans instead of Americans who happen to be Republicans and Democrats.