What is outcome bias?

Judging a decision by how it turned out, instead of whether it was smart when you made it.

An 80% bet that misses was still a good bet, that's just the 20% arriving on schedule. A 5% flier that hits was still a bad bet that got lucky. One result tells you almost nothing about the decision; only a long scorecard does.

It's why forecasters grade themselves with a Brier score across dozens of calls instead of celebrating single wins, and why a forecast journal beats memory: written reasoning can be judged on what you knew at the time, which is the only fair court there is.