The Miami Marlins present an interesting situation for a team that has won 2 world series in a relatively short history.
It seems odd that, with such rich high school and college talent all around that area, and with a baseball crazy, Latin American population, that this team isn't more supported. I've heard of two possible reasons for this:
1. With such a large transplant population in south Florida, many people are fans of the teams from the cities/areas in which they moved from
2. A large portion of their would-be fan base is basically in revolt from the previous ownership, who sold off mega All-Stars and MVP talent such as Christian Yelich and Giancarlo Stanton among others. Can you image how good they "could have been" with all that talent still there? They fans are furious over this.
3. That hideous new stadium where they play and how the community basically got screwed in trying to come up with the funds to pay for that place.