Preheat the oven to 450 degrees F (230 degrees C). Prick potatoes several times with a fork; place onto a baking sheet.

Bake in the preheated oven until potatoes easily pierced with a fork, 50 minutes to 1 hour. Remove, cool, and peel. Reduce oven temperature to 400 degrees F (205 degrees C).

Cook bacon in a large skillet over medium-high heat, turning occasionally, until evenly browned, about 10 minutes. Drain on paper towels; crumble.

Lightly grease a pizza pan.

Combine pizza crust mix, water, and oil in a large bowl with a fork until dough comes together; turn out onto a lightly floured surface and knead until smooth and elastic, about 8 minutes. Let stand for 5 minutes. Shape into a flat circle; place on prepared pizza pan. Build up edges slightly.

Bake in the preheated oven until crust firm and begins to brown, 5 to 6 minutes.

Toss potatoes with butter, garlic powder, and Italian seasoning in a large bowl. Combine sour cream and ranch dressing in a small bowl; spread over crust. Top with potatoes bacon, onions, mozzarella cheese, and Cheddar cheese.

Bake in the preheated oven until cheese melted and lightly browned, 15 to 20 minutes. Let stand 5 minutes before cutting.