He didn't knew this was coming? I knew it was the best card they had and I am an idiot. He (and I presume company) made no provisions for this?
Well it’s not happening so obviously he did...
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Since the indictments were filed in a DC court, and even swamps like DemocracticUnderground were bragging that POTUS' kids had been indicted, I believe he knew but they had to wait for due process. (Possible that the DS had also threatened him that such indictments existed). The AG wouldn't have a reason to pull indictments unless he had evidence that RR and Mueller were acting in bad faith.
Once Barr had time to take full stock of the ongoing investigations (see #2776), he was in a position to pull the indictments. Prior AG's didn't have the opportunity to question Mueller during an ongoing investigation without being accused of "obstruction".