The States’ cases so far have depended completely on ignorance, emotion, and suppression of exculpatory evidence. Mosby rushed into this without realizing her entire program would collapse if defendants chose Bench Trials to evade lynch mobs of their peers.
Does conducting her own investigation expose Mosby to personal liability in the various lawsuits filed by the officers? (And Schatzow and Bledsoe?). Smarter heads than theirs might want to mitigate their own exposure by stopping trials for which there is no hope of a conviction, and that seem to produce more evidence of misconduct with each repetition.
Yes, but barely. As DA she has near absolute immunity for charging decisions, but she can be found liable when she forays into investigation, which is not the DA's core function. That said, she can bring a turkey of a case using outside evidence, and the only remedy is to reject her charge following the presentation of evidence at trial.
Moseby did approximately what Angela Corey did to Zimmerman. Mount a political prosecution that flies in the face of the evidence. The legal system totally relies on good faith on the part of judges and prosecutors, and when that is absent, the system has no practical means of internal correction. A finding of innocence "cures the problem."