The CFA is geared towards practitioners. In contrast, Ph.D. is primarily intended as training to be a researcher. So, the natures of the programs and their approaches are distinctly different from each other.

Some doctoral programs require an MBA before entry, but quite a few don't. In fact, the best preparation for getting a finance Ph.D. isn't an MBA. MS in Finance, MS in Econ or a masters in math, engineering or physics (there's a LOT of math involved at this level) would probably prepare you better.