The UK broadcasting rights for the Superbowl probably come cheap. The subscription satellite channels will have spent most of their budgets on Premier League football and other major events, such as Test Match cricket. That leaves 'minority' sports available cheaply for whoever wants to broadcast them.
An analogy:
If you ask people how their local council(s) can improve their services, you'll be flooded with demands for more police on the beat, more local fire stations, longer library opening hours, etc, etc. But if you then ask people what should be cut to fund those services (or whether they'd be prepared to pay far more in Council Tax) they're usually not so quick to speak out.
Similarly, if you ask people what the BBC should be doing they'll want fewer repeats, more costume drama, the retention of local radio services, better coverage of UK sport, etc, etc. Yet when you ask what should be cut to provide all of those things (or whether they'd be prepared to pay a far higher licence fee) they suddenly go quiet.
Chris