One game is a small sample
Basketball outcomes swing on a few dozen possessions, and possession quality fluctuates for reasons neither coach controls. Over seven games, that noise averages out and the stronger team almost always advances. Over one, the noise is a genuine competitor. This is why bracket chaos is not evidence that the sport lacks a hierarchy; it is evidence that the format does not measure one.
Shooting is the wild card
The most volatile input is outside shooting. A team that shoots well above its usual rate for one afternoon can beat a substantially better opponent, and no defensive plan reliably prevents it. Teams that rely heavily on the three-point shot are therefore both more likely to cause an upset and more likely to suffer one, which is a trade-off rather than a flaw.
Reading the result correctly
The honest interpretation of a first-round shock is that a plausible outcome occurred, not that the favourite was overrated all along. That framing is less satisfying than a narrative about fragility, and it survives contact with the next season far more often.