Worked to stoke voter fraud mania? Probably. I doubt they relented due to a cooperation agreement because that would require an indictment or a plea deal or grant of immunity. It's not clear at all what proceedings, if any, reversed their decision. Nor do we have any idea what basis they used for the charges in the first place. I don't typically go for conspiracies but given the vagueness of the charge and the timing of the charges being dropped, I'm leaning towards this being simple prosecutorial overreach possibly due to political pressure.
https://news.ycombinator.com/item?id=33099707