The reason why noise is so high as you suggest is that wanted
informative signal is so damn low.
Hardly anything is ever really discussed beyond a few guys grunting one
liner sentiments.

This group ain't the land of the cultured intelectual with a thousand
words to say about everything.
Mainly leg tired physical types who are also brain tired after all that
pedaling.

Moderated groups are usually the most boring places to be. Imagine going
to the Pub With No Beer every night.
Everyone is polite, nobody is challenged, nothing contentious is ever
raised, and the women sit around knitting.

The lack of the moderator keeps the boring morons away. You just can't
get away with bullshit here because some bastard will call you an
arsole.

Its self moderation, plain and simple.