It wasn't because they didn't like the new F-150. I spoke to the head of the Harley design group over a year ago about it.
Its because they want Harley-Davidson truck owners to have unique, limited production trucks. Each year they made changes so it would be unique. They found that many people were asking about having a package for the heavier trucks, with 4x4. The decision was made to step up to the larger trucks to add more to the package and make a change to provide the limited package owners want.