Well, I'll go along with you that you rarely hear Montrose on the radio, anymore (and that's bullshit, compared to what does get played. Once upon a time, radio stations were stockpiles of albums. Now they're stockpiles of selected songs). And maybe you never heard them where you were at. But back in the day, I heard them plenty in Philly and St. Louis ('70's and 80's).
The point is, Sammy was hardly a stranger to success before VH. And I would 100% agree that he didn't need to join VH to stay in the scene.
If I'm remembering the story right, Sammy basically muscled one of his songs into the movie, "Heavy Metal". The producers let him in because you don't **** off Sammy Hagar. Again, this was before VH.