OK, it's luck or randomness. But apparently it's a form of luck or randomness that can be sustained for a long time.
If I'm flipping a coin it might come up heads the first 5 times in a row, but if I keep flipping it will correct to 50% very quickly.
A good hitter might be able to hit .400 for 50 games, but he will regress to .300 by the end of the season.
But a team who beats their Pythagorean record by 5 games might very well do it again the following season.
The correction factor seems weak to me. That is my real point.