It wasn't a physicist who found an application for radio waves though is the thing.

It was someone looking to monetize it somehow, who also happened to be a scientist in a different field.

Now, would someone else maybe eventually look into using radio waves somehow? Probably. But when the physicists are saying "neat, but useless", it'll probably delay such discovery even further since there's only one motivation, not two. Not to mention, said scientist would now have to convince the community to give them materials to look into this radio waves thing that physicists think can't be used practically. Materials which could be used for something else that could be deemed more important at the time because it's use might already be known, like bridges or infrastructure or just electricity wiring in general.