Regarding Trump vs. Biden, if you choose not to decide, you still have made of choice:
This thread could be a useful discussion, but it largely has fallen back into predicable railing against Trump and his supporters (a reasonable approach, but not really productive anymore).
As for the why, I don't think it's very productive to simply write off large portions of the population is inherently evil, even if they are very wrong in this case for pretty terrible reasons. I don't have a coherent reason for the why of Evangelical support for Trump, but I have a grab bag of possible reasons.
1. We're all pretty dumb, Trumper and non-Trumper alike. Even the smartest and most thoughtful among us have lots of bias in their thinking. The world is very confusing and complicated, particularly over the past 6 months or so. We come to conclusions and reason our way backwards. We all necessarily take many mental shortcuts and sometimes those shortcuts lead us to terrible conclusions. It takes a lot to overcome this, but we typically revert back to our identity rather than reasoning through problems.
2. This isn't a battle of ideas or even values, but one of identity. A certain portion of it is probably racial identity (white supremacy), but I suspect that left leaning folks overestimate how much this plays a role. Even the president of the SBC declared that "Black Live Matter because Jesus died for them." There are broader cultural identity issues at play here. Consider how this board frames the Evangelical issue: the people on the other side of the cultural divide would see most of this board in a similar negative light. The other side sees you the same way you see them because there is a cultural identity war going on. While there is a conflict of values and ideas, the ultimate conflict is in identity.
3. Trump thrives in this cultural war. He creates wedges where none are needed since they serve him politically. In one respect, he's right about the masks - they are symbols of political and cultural identity. Of course, Trump created or at least amplified this wedge, but it is no doubt there. This is why people are losing their minds over the masks. It's the cultural war right in/on their face.
4. Abortion and gay marriage. These are the elephants in the room that fit pretty neatly along party lines. This wasn't always the case. They are the ultimate symbols and catalysts for cultural identity. Regardless of the cynicism of the pro-life movement, particularly in light of the COVID-19 response, if you see abortion as equivalent to murder (or even much less, but still something profoundly wrong), it can be hard to get past the stark division between parties. There's a place to discuss whether or not the pro-life movement actually has an interest in abortion or just the wedge issue of abortion (I believe that it is largely a cynical movement among those in power), but there are still an astounding number of abortions that grieve the pro-life believer to the point where a deal with the devil might start to seem reasonable. We aways seem to just need one more Supreme Court Justice.
5. As for gay marriage, it's a similar cultural identifier. When the Supreme Court made their ruling, I remember the profound sense of mourning by many in my church the following Sunday. They weren't mourning the loss of their ability to control the lives of others; they were mourning that they believed that our country was turning further from God. The New Testament "clobber passages" about homosexuality discuss it in terms of a signifier of an increasingly sinful culture, so if you start with the Evangelical premise, the logic mostly holds up. The subsequent gay cake wars have only hardened the divide.
6. Many Evangelicals see progressive culture as openly antagonistic towards them. I'd say this is largely accurate and it's broader and longer lasting than the Trump phenomenon. Trump is the flashpoint because he's so objectively terrible, but he's not the only issue. Trump has taken up the mantle of the defender of Evangelical identity. Since he's taken on this role but also such an openly terrible person, we see the Bible twisting to declare him the modern day version of various terrible people from the Bible.
7. As a Christian who would probably be labeled Evangelical, the Trump movement has been despairing. Watching my Christian brothers and sisters turn to what amounts to an entirely different and worldly faith has been difficult. Idolatry is brutal and destructive. For those who are anti-religion, you can take some consolation in the fact that Trump has damaged the American church far more than he's damaged the country. Even as our country burns and dies, his movement has killed most of the American church. Much of it is preaching a false gospel and the rest is damaged by association.
In short, there's been a conflict of cultures going on in this country for some time. Trump has played this conflict masterfully and positioned himself as the defender of the faith (Fidei defensor) and the standard bearer for one side of this conflict. The fact that his personal values don't seem to align in any way with the faith or side he defends is almost irrelevant. He is going on the offensive in the culture war and winning victories. When it feels like the broader culture is so against you, this can feel cathartic. Yay team!
There's a certain irony in a faith that places so much focus on the end times and staying on God's side deciding to cast aside their values to win a worldly battle led by someone such as Trump. Abortion, gay marriage, and other cultural changes were seen as a sign of the times and they've indirectly led us to a leader that has brought both the country and the church to the brink. The pro-life movement led us to more death while doing little to curb abortion. Some might see what's happening as a judgement of God against the worldly church; others might see it as karma or the simulation breaking down. Whatever it is, it's some great dramatic writing.