You're looking back at history with rose coloured glasses. When the Reds were admittted it was on the back of large crowds, in excess of 20,000, going to the WACA to see NSWRL Premiership games. When the Reds entered the ARL they got 24,000 to some games at the WACA.
In 1996 the average for the Reds dropped to 8,200.
NRL Premiership games have been taken to the rectangular Perth Oval. The last six games that were played at that ground in 2014, 2016 and 2017 saw a sharp decline in attendances.
6,258 01-Jul-2017
11,433 21-May-2017
11,109 16-Jul-2016
13,142 05-Jun-2016
20,267 07-Jun-2014
12,014 29-Mar-2014
https://afltables.com/rl/venues/perth_o_gm.html
This shows interest in the game over there has dropped significantly. The Nines this year was a failure.