From what I can gather, people who know more American politics than me will tell you that, to a degree, the Democratic Party brought the last four years on themselves and so, to an extent, you're right. Complacency by the progressive, liberal side (which qualifies as the left in America) in the 90s and 00s created the situation which led to Trump - I can remember the Tea Party being ridiculed when it first emerged, but so much of what they were for formed the basis of what the Republican Party is today.
However, Trump is a one off, if someone like Mike Pence had been President for the last four years, I'd say he'd probably have been starting his second term now, but thankfully, enough people realised that Trump transcended left and right barriers and was both dangerous and not up to the job. Even in defeat, he's proving his unfitness for the Presidency by acting like the sort of despot you may see in a South American country who refuses to accept defeat and holes themselves up in a bunker claiming the vote was rigged- Trump demeaned America and now he's demeaning democracy.