I think it's utterly transparent and has been the plan for a while. Hence Johnson and the Cabinet trotting out the line "need to wait for the outcome of the inquiry" like broken records.
Police report will find insufficient evidence for a prosecution, the inquiry will find Johnson broke the rules and took the ****. But it'll be caged in far more diplomatic language than that, and it'll take months.
By which point spring will have started and they'll be hoping COVID will be pretty much over (as far as they're concerned, tough luck if you're vulnerable). People won't care as much, his rebels will have run out of steam and Johnson keeps his grubby little grasp on power.