One thing which strikes me immediately: time interval is short, a variance will be huge; this is on top of basketball being a fairly high variance game in general. I am not sure about NBA specifics, but it's plausible to me that teams play less than one game on average (or less than a few to be conservative) in a given week.

• So some teams with stellar players might not play at all!
• And most players will be judged based on one game.

This might be due to top players having much larger play time? If you only look at super-scorers beating best players you get 25%. If you look at "supers" beating best and second-best you get 15%.

Nice; I think I don't have much to add here.

My default explanation was that availability bias is at play.

Per https://en.wikipedia.org/wiki/Availability_heuristic

Availability bias, is a mental shortcut that relies on immediate examples that come to a given person's mind when evaluating a specific topic, concept, method or decision.