In a closed league, average results long term = average crowds.
People seem to perceive WSW as one of the bigger clubs due to their early success and fanbase, but on field that's definitely not the case. They have basically been very average consistently for decade. That takes it's toll. The ACL win was epic but it was 10 years ago and they haven't won silverware of any kind since. Look at the total regular season points earned since WSW started. We have SFC at the top then a bit of a gap then we have MC, MV and AU all on similar numbers, then another gap and then we have WSW and BR followed by the other average performing clubs. WSW are top of the average group but still very much average. Very similar story at the Roar, so no surprises the crowd numbers a similar. Doing enough to avoid the bottom group but not enough to be genuine contenders. Tough to rally a crowd around mediocrity. At least when a club is consistently poor they gain the underdog status which makes it easier to rally support.
Still early in the season though. Plenty of things can happen. If WSW finds some consistenct form (especially at home) the crowds will return.