You see.. I don't really know if that falls into the category of bandwagon fan. That's not jumping on that team's wagon for their success and popularity but mainly so they (let's use Seattle v. Denver in this case) destroy your hated rival. That's not bandwagoning imo. That's special circumstance. For instance, made up scenario, if I am rooting for the Raiders to beat the Jets in Week 17 so the Jets don't make the playoffs, does that make me a bandwagon fan for the Raiders?
Both of these scenarios in the end have your team benefitting so technically I wouldn't call that bandwagoning.
I hate always hated Miami since the Big 3, so I didn't care who made it out of the West I would just hope they beat Miami. I wouldn't get any satisfaction from SA winning, just the satisfaction of Miami losing. So I wouldn't call that bandwagoning.
Bandwagoning, at it's worst, is all of the Denver Broncos fans who used to Colts fans. Or a random person throwing on a Russell Wilson jersey. Or any Yankee fan with absolutely no ties to the team or NY just simply liking them because of their prestige. Something of that nature.
Miami has the biggest bandwagon fanbase but this is mainly because the league is player oriented so fans tend to follow a certain player (aka Lebron or Melo, etc..), which I don't do, so I cannot comprehend that. I could get the Cleveland LeBron fans following him to Miami but not the rest of the world.