Did Trump prematurely declare victory while the outcome was uncertain?
Yes. In the early morning of November 4, 2020, with key states like Pennsylvania, Michigan, Wisconsin and Georgia still undecided and neither candidate at 270 electoral votes, Donald Trump claimed at the White House that “frankly, we did win this election” and spoke as though he had already won. Fact-checkers and news outlets characterized this as a premature and false declaration of victory based on incomplete results. (amp.cnn.com)

How did equity markets actually react?

Overnight futures:
– A Reuters report on S&P 500 e‑mini futures noted that after Trump claimed he had won while many votes were still uncounted, “U.S. stock futures turned down” and the S&P e‑mini contract fell about 1.15%, reversing an earlier gain of roughly 1% made when Trump appeared to be winning Florida. (mix929.com)
– Nasdaq 100 futures gave back part of their earlier rally but remained up (~0.8%) even after the speech. (mix929.com)

So there was a brief, modest pullback in futures, not a multi‑percent crash or limit‑down “panic” comparable to major shock events.

Cash market afterward:
– By late morning on Wednesday, November 4, 2020, U.S. stocks were strongly higher: the S&P 500 was up more than 2–3%, the Dow around 1.7–3%, and the Nasdaq up about 3.8%, as investors focused on the likelihood of a split Congress and the perceived benefits of gridlock. (fortune.com)
– Coverage described markets as “soaring” and “sharply higher” despite the ongoing uncertainty and Trump’s premature victory claim, emphasizing that Wall Street largely looked past the contested‑election risk in favor of the policy outlook. (fortune.com)

Assessment vs. Chamath’s prediction
Chamath predicted that if Trump declared victory on election night while the outcome was still unclear, equity markets (e.g., futures) would react with panic and a sharp selloff shortly thereafter. What actually happened was:

• A short‑lived, roughly 1% dip in S&P 500 futures from earlier gains after Trump’s statement, followed by
• A strong rally in the cash equity market later that day and in subsequent sessions, with no sustained panic or sharp multi‑day selloff tied to the declaration itself.

Given that the move was modest and temporary and the overall market response was strongly positive, this falls well short of the “disaster scenario” and “panic” Chamath described.

Therefore, the prediction is wrong.