Rudy Giuliani was the SDNY US Attorney at the time.
It's not hard to figure out what that reason was.
Mueller was the USAG at this time & Rod Rosenstein was on Mueller's team.
Keep watching, this is going to be awesome.
People who think Trump only learned the intel game once he started running for President = clueless.
Pants are filling all over that town now that Mueller reached his inevitable conclusion & they are watching Barr come in.