umm.. Don, they're not ignorant. They are VERY informed and not only did they vote for Trump in 2016. They are going to vote for Trump disproportionally higher in 2020. The idea of being white is more valuable than anything else on this planet.
You overestimate his base. Trump was marketed as a populist candidate for a reason. He appealed to lowest common denominator whites, luring many of them in with the promise of (blue collar) jobs and a return to American "greatness". Vague promises that he's proven himself unable to keep. Vague promises that any reasonably intelligent individual already knew were untenable. The majority of them aren't informed at all, let alone "VERY". That much was clear just by them buying into his bullshyt. The only people left now are the ones who will fully and KNOWINGLY vote against 100% of their interests in favor of being white. And believe it or not that number is dwindling.
You also forget the number of young whites who flip-flopped from being Bernie Bots to "pedes". Within months they went from supporting a socialist liberal candidate to throwing on MAGA caps in support of a nationalist conservative. The two had disparate ideologies but those voters didn't care. They were "fanboys" in it for the culture and the drama of being a contrarian.
Now obviously this doesn't mean folks won't come out in full force in 2020, but again...you truly overestimate his base. The majority of those who would blindly support him already did so in 2016. Literally none of them sat out the election, they've pretty much all been accounted for save for the fresh 18's voting like daddy taught them too. But mostly, that well has run dry.
Trump couldn't even secure the popular vote and many of those who voted for him are disillusioned.
You forget that millions sat out the election (on BOTH sides) because they couldn't stomach either candidate. From the Republican #NeverTrump-ers to the ambivalent dems who couldn't stand Clinton. Those groups - both of which still hate Trump - will be the ones who truly come out in 2020 at disproportionately higher rates because they see now what staying home gets you.