I think you and the author fail to realize that variance in an outcomes doesn't transfer to variance in an expectation. If you make the error bars around Trump's numbers larger in both directions, it doesn't change your guess if you're trying to minimize your expected error.
What you and the author are implicitly saying is that the only certain thing was that Trump's upper tail decreased over time. The betting markets and I disagree with you. Did Trump getting COVID increase his vote share or lower? I have no idea. It's a coin flip. I have no idea what the aggregate thinks/thought. The coin flip changes the variance of the outcomes possible but it doesn't change my guess of Trump's voter share.
You should review stock behavior around binary events like Apple v Samsung lawsuit. Just because the outcome is uncertain, it doesn't mean the stock jumps wildly from pretending they will win to the next minute treating it like they might lose. Your criticism is akin to being surprised that the price is neither 0.00 or 1.00 because someone can't "40% win".
Wouldn't Trump being diagnosed with Covid be more akin to the first (or second) 737 Max crashing and its effect on Boeing? This was not an expected outcome and would be likely to shift the entire distribution of outcomes. If you're going to argue that it truly kept outcomes identical, then I would likely just disagree with your forecast and call it a day.
No, I think the outcomes changed. I think the outcomes changed to be more chaotic. I can generate two possible narratives that seem plausible to me:
1) Republicans change their opinion after seeing the President getting Covid and realizing their vulnerability.
2) Further entrenching their belief that if the President can recover, so can they.
In reality, I think both narratives apply to different populations. The question becomes how many people changed their belief and how many didn't. I think 50/50 is a fair (and simple) assumption that doesn't change your expectation of the election.
With regards to your Boeing example. Seeing multiple bad events clearly negatively impacts Boeing. But Trump getting Covid is not clearly a negative to his election chances. You would have to convince me by polling many Republicans to see how their views changes pre/post Trump getting infected. Without having polled the people, I think a 50/50 split is a fair assumption. Of course, I would update my belief in the presence of relevant data.
What you and the author are implicitly saying is that the only certain thing was that Trump's upper tail decreased over time. The betting markets and I disagree with you. Did Trump getting COVID increase his vote share or lower? I have no idea. It's a coin flip. I have no idea what the aggregate thinks/thought. The coin flip changes the variance of the outcomes possible but it doesn't change my guess of Trump's voter share.
You should review stock behavior around binary events like Apple v Samsung lawsuit. Just because the outcome is uncertain, it doesn't mean the stock jumps wildly from pretending they will win to the next minute treating it like they might lose. Your criticism is akin to being surprised that the price is neither 0.00 or 1.00 because someone can't "40% win".