I preface this by saying some of the most bogus information out there begins with the words "A recent study says _______". So a grain of salt is needed.
Not surprised by the Raiders being near last. They moved away from their original fan base, they then moved away from their new fan base, a not insignificant portion of their fan base had grown real tired of Big Al's handling of the team, they haven't had much success in quite a few years, they tried to push some of the most outrageous PSL terms (fail!), their fans get treated to what is likely the crappiest stadium in all of football (possibly all of Pro sports), they have been second fiddle in their own geographic area for most of the years they have been back in Oakland. Just isn't a lot of positives for the Raiders fan base other than their far removed past glory.....