[draker]

It seems like "won handily" would be more appropriate. I searched within the linked book and the only result for "handedly" or "handily" was one occurrence of "single-handedly".

Surprisingly, when you Google "won handedly" (used Incognito) the tenth result is that book.

Within Google books, the query "won handedly" returns 26 results; the first being the linked book as well as another The Michelin Men: Driving an Empire.

I would assume that phrase is used in the books, but if not the text possibly an image from one of the ads?