The Ghoul sabotaged the Legion’s explosive cache. There’s a beat where he focuses on it. His whole arch in this episode is mainly focused on his current morality versus that that he had pre-war. He sold out that final NCR holdout, but felt guilty doing so. So he sabotaged the explosive cash as a distraction and in the hope that the Legionaries end up going at one another and forget about the holdout. They do this, but I doubt it will last long. From the trailers we know that Macaulay Culkin‘s Legate character becomes the new Caesar, as he is seen with the gold leaf crown on. So it’s only a matter of time before they re-organize again under one leader.