Why did POTUS meet with Mueller?

This has been bothering me for a while. We know that Mueller couldn't and would never have been given the Director of FBI position.

From POTUS's perspective and plan, was there a legal reason?

This Bloomberg article says a few things.

"Trump and Attorney General Jeff Sessions, who attended both meetings, were blindsided, according to a person familiar with both meetings. The president immediately blasted Sessions for not knowing the announcement was coming and challenged how the person he’d just interviewed for the FBI job – and who Trump said had a past dispute with him over golf club fees – could now be investigating him, the person said."

What really stuck out was this quote for Giuliani:

“If a guy just turned you down for a job, it certainly creates a question as to whether you could be perfectly objective in making an important decision about that person," said Trump’s lawyer, Rudy Giuliani, who said there are additional conflicts the legal team is aware of but not making public.

We have to assume that POTUS and Sessions knew that Mueller was going to be appointed to lead the SC. No fucking way they were "blindsided".

"Deputy Attorney General Rod Rosenstein, who appointed Mueller and supervises his investigation, has testified he is unaware of any conflicts of interest that would disqualify Mueller from the job."

So by having this meeting, did they create an obvious conflict?

Was there something else?

Also, I remember reading that RR attended the meetings as well. Can anyone verify that?

https://www.bloomberg.com/news/articles/2018-08-03/trump-fury-over-mueller-conflicts-dates-to-oval-office-meeting