Extreme results tend to be followed by more average ones, for no special reason
Francis Galton found that unusually tall parents tend to have somewhat shorter children, and unusually short parents somewhat taller ones — not because of any active correction, but because extreme measurements are partly luck, and luck doesn't repeat. The same statistical pull explains why a rookie's stunning first season is usually followed by a merely good one, and why yelling at someone after a bad performance looks like it 'worked' even if yelling did nothing at all.