You are not the middle. No matter how much you want yourself to be, your posting pattern screams of "I want the middle to be farther right than Goldwater". Even if you don't vote for Trump, which of course you will if he is the guy on the ballot, the people you would be voting for are just as right and fascist as he is. And probably better at it since they wouldn't self sabotage like he does.
As for why independents aren't supporting Biden...I don't know. I know a big part of his drop is because he hasn't started carpet bombing Israel yet for defending themselves against a terrorist attack from Hamas, but I wouldn't call those people independents. For independents, I suspect there are many reasons for that and the wording of the question probably matters as well. Democrats have been busy doing what Republicans refuse to do, and that is to actually do their jobs and govern. They aren't campaigning yet. Republicans have been campaigning since 2021. They needed to switch the topic as quickly as they could so people would have something else to talk about other than how their party just tried to overthrow a free and democratic election. The fact that they got their asses kicked in 2022 hasn't even gotten them to change a beat. It isn't important to them if the message is convincing voters, it is important to them that they stay out of jail. As long as Trump remains the focus for those investigations and trials then they are relatively safe. I have started to hear grumblings of the investigation arrow pointed their direction though so it is likely they will see something during a second term if Biden wins.