An interesting nuance that came out in the investigation might explain why Urban is in trouble at all.
Mary Jo White explained that (1) Gene told Urban about 2015 and (2) neither of themtold compliance. Ok, well we could ask, why was that Urban's responsibility at all, given that his superior was the one who told him in the first place. The lynchpin seems to be the wording that bridges (1) and (2): that they monitored the criminal investigation and discussed it for a series of months.
If it hadn't been for that, if instead they had only had one interaction about this with Gene relaying the info and then "get out of here, Urban, I'm taking over," I think Gene would have been fired for cause and Urban reinstated. But instead, the two of them went on to a phase of shared stewardship of the allegations. And both knew (and perhaps waffled over the fact that) Compliance was never called.