Setting aside the criticism of his opinions...I would assume he must be a skilled writer. One that tells his version of the story in a way that engages the general public (at least the minority that would even consider reading history). He must sell well...relative to this standard...based on how often I see his books.

From there it's a short hop to TV interviews...if your books sell well. I know Doris Goodwin, who wrote a bestseller about Lincoln recently, gets to be on all kinds of TV shows to give her opinion about all sorts of subjects.

My first introduction to the French Rev was _Paris in the Terror_ by Stanley Loomis. No friend of the Jacobins, but he was a good story-teller...he made it dramatic and kept my attention...even though I found his "bad guys" more interesting than his "good guys".