We have seen this movie before... Gawd I hate reruns...
You Trumpees like to imagine that if Trump won in 2016, then therefore he can't possibly lose in 2020, but thats not a rational conclusion, that's just magical thinking.
National polling was dead on (+3% polling average vs +2% votes for Hillary outcome). This national polling was showing much better numbers for Trump in 2016 than they are now.
Rassmussen, a Trump favorite who he hailed as the most accurate in 2016 election, is showing him down by 12% to Biden after Trump's disasterous performance in the last two weeks. This same polling outfit was showing Trump and Clinton in dead heat around this time.