It's one of those Frankenfood creations that had existed in some shadowy form long before Pizza Hut announced it as a limited-time offering for the United States in June — Japan got a version of it from Pizza Hut in 2006, with full hot dogs in the crust, and both Pizza Hut and Domino's brought it to the United Kingdom earlier this decade — and it mashes up two things, pizza and hot dogs, that are both understood as quintessentially American and Bad For You.
That's the value proposition of fast food: Everyone "knows" that it's Bad For You, of course, and still people want to eat it, for convenience or novelty or flavor.