It was not until I witnessed the surprise of large numbers of Democrats at Biden's debate performance that I realized that they actually were surprised.
I know this is very hard to comprehend. As you say, it has been obvious all along. It was obvious to me back in 1991 when I first noticed Biden during the Clarence Thomas hearings. I knew immediately what Biden was.
Those who were actually surprised have been deep in denial, blind and also stupid to allow themselves to be blinded.
When I first read Oedipus Rex as a teenager, I thought the tale absurd. Of course the relationship of Oedipus and Jocasta was obvious. It was not until I read Sigmund Freud's analysis that I understood the profound depth and universality of the tale. They knew it all along, but they were deep in denial! We are all capable of the most breathtaking denial!
Since I understood this, I have been reminded of the power of denial many times.
One example, of many, was when, as a resident at Duke University Medical Center, I examined a man with carcinoma of the penis. The carcinoma was the size of a cauliflower. When I asked how long it had been present, he replied: "A couple of weeks." Of course it had been present for many months at least.
The reaction of many Democrats to the debate was an eye-opener for me. I had believed that their support for the Democrats resulted merely from cynicism, mendacity, and greed. But I really think many Democrat supporters are actually surprised and were shocked out of their denial by the debate.
Do not expect a conversion to wisdom and clarity from them. Theirs is a propensity for bad judgment, as they have amply shown.
Of course, many Democrats are motivated merely by greed, cynicism, and mendacity. Certainly those in positions of power and influence are. But what else would anyone expect from the party of slavery and infanticide, among many other evils?
If they are surprised it is because they are not paying attention as in why bother there are better things to do and other distractions to pursue. This leads to being easily misled.
The MSM put a lid on Joe's cognitive decline. If it was brought up it was portrayed as a conspiracy theory. MY local newspaper and TV stations didn't cover it. National news gets fed to them by the major networks. My aging parents read the WSJ and watch FOX. They had no clue he was senile in 2020 until I mentioned it to them..
Interesting perspective.