We never had 500 'active'.
Like the Fever Zone alot of people were 'adjacent' rather than 'active'.
There was however a time at the end of the Rufer season at Ericsson stadium where you had to get to the ground 45 - 30 minutes before kick off in order to get a place in the back 10 rows of the Bloc. But yeah, 20 - 30 actives (at best), and several hundred adjacents ... but the actives need adjacents...
...500 odd singing and jumping up and down and generally going mental is still 500 or so, and the collective buzz is strong.
It does need coordinators, ring leaders, caporegimes etc though to focus the will of the masses.