All that we know for sure about what the jury believed is that that they concluded, quickly, that the State couldn't prove beyond a reasonable doubt the baby was born alive. The three most serious charges were all predicated on a live birth. No live birth, no conviction.
Beyond that, the defense made a compelling case, imo, way beyond what was required to establish reasonable doubt, that the baby was stillborn.
Check out Dr. White's testimony, Magnolia, if you want to get to the core of the case.
As a more granular aside. Skylar freely told the DR she visited in July that her baby was stillborn and that she had buried her in the backyard. Skylar's aunt worked for that med practice, btw.
The DR testified at trial she believed Skylar that the baby was stillborn. (State objected, judge sustained). I don't think it was testified to at trial, but that DR and another from the practice said the reason they notified LE wasn't because they believed Skylar had harmed, much less killed her baby, but they concluded they needed to ask LE what the protocol was about reporting the back yard burial.