The police force is dependent on the government for funding and for agreeing to various measures requested by the police (eg the current request that special constables be allowed to carry and use tasers). So, in my opinion, they may well be disinclined to look too closely for any possible wrongdoing by a prime minister. Additionally, as has been said, police officers must have been aware that these get togethers were taking place but they did nothing to intervene. Much easier to fine ordinary young people £10,000 for arranging a snowball fight outside than to confront people in high office. Sue Gray is a senior civil servant, so not exactly an independent assessor and, in any event, even if she makes more critical comments, some areas of the mass media will just point to the police report as being the final word on the matter.
It is said that the police felt it unnecessary to name any individuals who have been fined, and it seems therefore a possibility that some people insist they were not found to have broken the rules, when in fact they were. After all, Johnson quite vociferously stated on several occasions that "no rules were broken", when it has been reported that he "popped in" on some of these occasions so and so must have known what he said was a lie. I don't understand why "popping in" is not still considered as breaking the rules. Apart from his individual responsibility, as prime minister surely he should have insisted that these events be called to a halt?
I think Johnson is an absolute disgrace and, by association, the majority of his party.