Many more people turned out to vote for democrats in 2008 and 2012. Clinton just didn't inspire people the way that Obama did. At the same time, Trump had a way of turning out people to vote for him that might not have otherwise shown up to vote for a Republican.
One of the key reasons that resulted in a Republican win was the Republican stance on immigration.Many American citizens are concerned that the government is not doing enough to tackle illegal immigration. The Republican's said that they will take a much tougher stance on illegal immigration.The Democratic party should have followed the Republican stance and take a tougher stance on immigration. Also Hilary Clinton was not as charismatic as Trump.
People showed up to vote. Nearly 3 million more people voted for Hillary Clinton than for Donald Trump. The problem wasn't voter turnout. The problem was leaked emails, the FBI getting in the way, the Russian interferance, and the electoral college. Clinton won the popular vote by an outrageous margin, and should have been awarded as the winner.
No, I don't believe that Democrats lost the election because they didn't come out and vote. I believe that there are several reasons that Democrats lost the election, the primary one being that Hillary Clinton was not a popular candidate. She was followed by too many scandals and was viewed by many as an establishment politician. Americans are tired of the status quo.