I note that you’ve moved from Trump supporter to Trump voter. That makes it possible–though I would argue increasingly less plausible over time. And I’ll assume you mean in 2020, not 2016.
Ignorance can do a lot. However, there is some degree of a moral imperative to at least try to be informed before voting. It’s also less and less plausible that they could not wind up informed about the bad things Trump has done.
There are also a lot of people who are actively choosing to delude themselves, and I believe that is immoral. They have misgivings, so they surround themselves with only that which will tell them those misgivings are wrong.
There’s also a moral imperative to care about other people more that yourself. So any argument about the economy being good “for me” is not a moral position. If they refuse to wear a mask because “you can’t make me”, they cannot be a moral person.
I also hold Christians to their stated morals, and we have requirements in the Bible for leaders. And there is a biblical imperative not to add to God’s word. So, i ftheya re sola scriptura, and they put abortion above the things that are actually mentioned in the Bible, that is immoral. (Though I will allow for ignorance due to people lying to them about that issue.) The stuff about caring about others more than yourself applies here, too.
I can imagine someone so utterly misinformed that they, despite being moral, voted for Trump. It’s an uphill battle to climb.
That said, a supporter is different. A supporter is someone who is still supporting Trump now, even after the vote. And Trump is staging a coup. He is trying to overturn an election. Over 80% of America acknowledges Biden won—so quite a lot of Trump voters are no longer supporters.
I will also note that “disagreeing” is not a get out of morality free card. Ignorance can be, but disagreement isn’t. The reasons not to support Trump are factual, and not subject to disagreement. Just possibly not knowing about them, or being convinced they didn’t happen.
For example, disagreeing about Trump’s handling of COVID-19 is itself an immoral act. Being ignorant about it isn’t, but, if you know that Trump specifically shut down a plan because he was sure it would harm blue states more, then your disagreement that this is bad is immoral.