A major development in Roger Stone's case may explain why Mueller is finally resigning

While the substance of Special Counsel Robert Mueller’s remarks on Wednesday are receiving the bulk of the press’s attention, there’s a curious question that arose from his statement that has yet to be answered: Why did Mueller only resign now?

Mueller had officially concluded his investigation on March 22, when he delivered the final version of his report to Attorney General William Barr. After that, Mueller stayed on at the Justice Department, it seemed, to help oversee the release of the report, reportedly helping redact significant sensitive portions of text. But once the report was released on April 18, it wasn’t clear what work was left for Mueller to do. It was only on Wednesday, more than two months after completing the report, that Mueller officially announced his resignation.

Another development Wednesday in a key case that had been under Mueller’s purview suggested a possible explanation for his final departure date. As CNN reported, a former Mueller prosecutor, Aaron Zelinsky, revealed in court Wednesday that a witness tied to Roger Stone has finally agreed to testify before the grand jury.

Stone is currently awaiting trial for the charges Mueller brought against him, which include lying to Congress, obstructing justice and intimidating a witness in the course of the Russia investigation. But there have been hints that there may be other charges looming over Stone, the most prominent hint being Mueller’s effort to get his associate, Andrew Miller, to testify before the grand jury.

Miller had long refused to testify, and he was held in contempt by Judge Beryl Howell for his refusal, but he has been appealing the decision. Now, it was revealed in court, Miller has agreed to testify on Friday. This suggests, though it is far from certain, that new charges might be coming against Stone. Zelinsky spoke privately with the judge on Wednesday to explain why Miller’s testimony was still needed.

The Miller testimony was one of the outstanding threads in Mueller’s investigation that was still pending when reports first suggested that the Russia probe was wrapping up. Mueller seemed to intensely value the testimony, going to aggressive lengths to force Miller to testify. It’s possible that the special counsel has had some role in the ongoing efforts to get Miller to testify, and once that he had finally agreed to appear before the grand jury, Mueller concluded it was time to step down.

However, as Vox’s Andrew Prokop noted on Twitter, there’s another outstanding thread in the investigation that has yet to be resolved. Mueller subpoenaed a company owned by a foreign country in the course of his investigation, and the company fought the subpoena all the way to the Supreme Court, where its appeals were denied. We still do not know what will become of that case, or even which country is implicated.