This city lives and breathes pro sports, as long as the pro sport you’re talking about is the NHL.
I think it comes down to this. Everyone loves the Ottawa Senators and it creates a pro sports vacuum. Once people get through a season of supporting the Senators, the NHL and their kids’ competitive sports and activites, I don’t think they have the time, money or energy to consistently support other pro sports.
It didn't help that the Rapidz were extremely minor league. They had shaky spending habits. They also had that weird, pointless decision to change their name and logo right before the season, not to mention the firing of a popular manager while he was away visiting his sick wife.
I still say a good, credibly run CFL team has a chance at showing up on Ottawa's sport radar. For the foreseeable future, everything else a big time long shot.