Generally there are two main reasons that you see product reformulations. First, there is a bunch of new research performed, either finding superior ingredients or new knowledge about pathway interactions. Second, there is a legal status change on one or more of the ingredients.
In the case of DCP, it's actually a combination of both.
TTA is undergoing final pharmaceutical testing and is no longer allowed to be used. As well, a lot more research has been done demonstrating that activating both PPAR-alpha and PPAR-delta, with as little gamma spillover as possible, leads to greater fatloss. DCP 2.0 is equally potent with DCP original.