The 80% is not the proportion of people who think he would win, that's not how these things work.

Every single factor was pointing towards Bolsonaro, Polymarket was just consistent with that.

He unexpectedly won the first round of the election. His lead was expected to grow since he'd likely get most of the votes of the other candidates. 17 out of 18 polls favored Bolsonaro. Market movements indicated a strong expectation of him winning. The Brazilian Real futures are already down 10% in the last couple hours.

But that's how democracy works, I think this election will be studied many times in the future.