You are making it out to be a counter conspiracy. It is/was not.
Mueller was just asked to run a legit investigation and let the evidence take him to the truth.
We all know who was actually colluding with the Russians and who attempted to rig the election.
No one was 'in on' anything, except that the good guys played the game based on knowing what a legit Mueller investigation would yield.
Mueller has distinct knowledge of the corruption because he was part of is for many years and the meeting with Trump was to let him know that there was only one way for him to avoid prosecution- RUN A FAIR and LEGIT INVESTIGATION.
Trump knew that the Russia Collusion narrative a sham from the beginning and he had nothing to worry about. He did not have to lie to anyone and if you want to cite Occam's Razor- you have to recognize that the simplest answer is that all Trump wanted was a fair and legitimate investigation into who actually committed crimes.