This is a small lesson in plant physiology, which applies to air-layering. You have a bark connection in your broken branch, but little or no woody connection. The woody portion supplies the water, the bark provides the products of photosynthesis. This is why the leaves are wilting, same as if you ave cut the branch off, because you lost the water channel to the leaves. This is also why you can air-layer many plants. By keeping the woody portion of a branch, ,you continue to supply water to the part being air-layered. By stripping a ring of bark, you are interrupting the flow of the products of photosynthesis and diverting them into producing roots for you air-layer, rather than roots for the entire plant.