Why wouldn't national sponsors want to be on Boston's successful country station other than their cozy relationship with iHeart under which listenership apparently is not a major factor?
They're buying two different things. Those national sponsors who specifically want to reach KLB's audience likely buy both. No law that says advertisers have to pick one or the other. They probably get a better deal on the Bull. My rule of thumb is when you can't sell ratings (because they're not good) you sell something else that makes up for bad ratings. iHeart has a huge digital presence.