I think a lot of them do see it, but he pisses off the libs and seems to be promising to hurt the people they want to be hurt, so they are OK with that.
Are we just going to forget about the family separation border policies? Or the "it's ok if grandma dies as long as we can go back to Outback Steakhouse again" treatment of COVID?
Also it wasn't Hitler himself that architected the Holocaust. Him being in power gave power to even worse people. He was happy to go along with it, it just doesn't look like he had any specific plans to actually exterminate the Jews when he was rising to power. So don't think that Trump's lack of any specific agenda means that such a thing won't happen if he is in a position to enable it.
For a way too large group, his being unhinged bigoted rants are a selling point, not a liability.
For way too many others, they don't care about his unhinged rants because he's pledging to hurt OTHER people, not them.
The former are bad, but aren't enough to sweep Trump into power. The latter, though, could help Trump attain power and then will act shocked when they get targeted.