Oh, I'm sure those people existed in 2016... but a lot has changed in four years.
Trump's main issue right now is precisely those people in the middle: the undecided, the easily swayed, the people who don't really talk about how they'll vote. In 2016 it made sense that there would be a chunk of people whose dislike of Clinton (or susceptibility to conmen) would lead them to vote Trump without broadcasting it in advance. But in 2020, that same group is not only considering a less contentious Democrat candidate, but can see that Trump is an abject failure.
I don't want to get cocky. But it's important to note that there are indicators for a Democrat win that weren't present in 2016, and that it really won't take much to swing things in Biden's favor.