Wasn't this the problem with their previous stadium?
The argument I always heard about the need for a new stadium was that people were not coming to the games because it was such a pain to get there. So what was the point if the new stadium, albeit closer, is still a pain to get to? It's not the extra 10 minutes driving that is the problem.
If taking public transit means multiple mode transfers (car-to-bus-to-rail-to-bus) and waits at each, few are going to choose it over driving. Best build some more parking, or forget it.