All these alternate theories require the DA to be a crook, or a foreign agent, or Hillary's robot-drone. That adds a layer of improbability that Occam suggests we cut away. The simplest answer is that she's a straight-arrow who was told to ditch this by someone she considered to be legitimate authority, and higher than her boss. There's a judge in the middle of this as well -- he had to go along with sealing this, and he would have been familiar with all the similar cases in the area, and would have known how unusual it was. That also points to "legitimate authority," unless we want to posit that the judge also happened to be a crook/foreign agent/Hillary robot. I think somebody with a Big Badge did this.