The A`s don't have a stadium because they want public money. Add a new stadium doesn't guarantee revenue. Nearly every team in the majors has a newish stadium now and many still aren't huge revenue generators. You have to have a marketable product, which doesn't necessarily mean just winning.

And the JLS site is available if the A's effort decide they want it. They need to tell the mayor what to do with regards to the site. And then build the park themselves.