Attendance was fine when the Marlins won it in 1997. The '97 firesale that was over a stadium dispute rather than anything to do with fan attendance, destroyed any care many South Floridians had for the team. The city of Miami loved the '97 Marlins and the city was betrayed.
They averaged less than 30,000 a game, they had tarps up in the first 2 rounds of the playoffs- the City of Miami didn't love them that much. The marlins ahve been above the NL avg in attendance for ONE season in their history and that was their inaugural year of 1993.