FROM MY COMMENT BELOW
It is my personal opinion that Mueller took Acting AG Whitaker aside when he first came aboard and explained the realities. IMHO one of those might have been explaining to Whitaker that any attempt by Whitaker to inform Trump as to the workings of the OSC could be interpreted to be an attempt to obstruct justice by interfering in an ongoing Federal investigation and his position and title would not protect him from becoming an additional target of said investigation.
Trump’s an idiot. Whitaker has probably found out that he’s not as smart as he thought he was and as big as he is physically, neither his size or his intellect can intimidate Robert Mueller. Mueller is combat tested Marine officer, Whitaker played tight end for Iowa. As to intellect, do we really need to point out Whitaker’s deficiencies? He deliberately said idiotic things to grab Trump’s attention.