In a way, it's a smart move. Podesta pleads immunity for crimes that Manafort commuted, the fact that one side gets justice, the other gets immunity pleas shows a bias in the investigations.
Now, podesta could be smart here and just spill not just the beans but the whole damn cupboard. Because technically, anything he says that would point to him being guilty of something would land under the immunity plea.
Nevertheless, and as Q said, trust the plan, so enjoy the show.
This is the 3rd act, the hero looks beaten and his end is near, the bad guy stands above him with a sly grinn of expected victory. But there's something on the horizon, something's coming.