This article from New Statesman has it spot on.
www.newstatesman.com/politics/uk/2020/05/if-dominic-cummings-not-sacked-boris-johnson-s-government-will-lose-all?fbclid=IwAR1Ne_5ffC66PWTMWTYmwl3ZTftHgCr1BjOqjMuVR6GERm4K2FYHm9ihnfo
'Johnson cannot sack him because he would be helpless without his svengali. He cannot keep him because his government would lose all its remaining credibility as it battles Covid-19. Cummings made Johnson.
Without him, the Prime Minister would be like a dummy without its ventriloquist, a puppet without its puppeteer.
Under no other prime minister in living memory would Cummings be allowed to stay in his post, but this scandal has ripped the mask off this government’s face. It has exposed its true nature – its shamelessness, its arrogance, its deceitfulness, its contempt for “the people” that it claims to champion, the utter cravenness of its ministers.
Cummings himself has displayed not a jot of contrition, He has mocked suggestions he might resign in a manner that suggests the Prime Minister has no say in the matter.
Locked in Downing Street, Johnson seems to have lost his fabled common touch. He seems not to grasp the blazing anger that Cummings’s conduct, and his government’s reaction to it, has unleashed – not just among yesterday’s Remainers but among lifelong Conservative voters and those blue-collar, traditional Labour voters who backed Johnson in such large numbers last December.
Johnson is like a man caught in a quicksand. The more he flails, the deeper he is sinking into the morass, squandering public trust and sympathy. The public might forgive his incompetent handling of coronavirus, but not this egregious lying and hypocrisy. Sooner or later he will have to sack Cummings. The longer he dithers the worse he and his government will be damaged.'