“Nullification” is the wrong word. Jury nullification means the jury voted to acquit even though the prosecution had proved its case. Here, we just need the jury to do its job and vote for an acquittal based on the lack of evidence.
I read an article in Politico recently about that grand jury. Apparently it was very politically motivated. They indicted people who the prosecutor had told were not a target. They apparently went off the rails. Some of the grand jurors said that there was a clique of jurors who just wanted to indict everybody. They’d ask accusatory questions and the other jurors would roll their eyes.