Cummingsgate: Why isn't Cummings going?

It is clear now that come hell, high water or Preston Guild, as they used to say when I was a lad, Boris Johnson is not going to sack lockdown buster Dominic Cummings, so unless Conservative MPs suddenly find the guts to remove Johnson, the 'adviser' is not going anywhere. But with 100 Tory MPs voicing their dissatisfaction publicly, and, we're told, many more privately, Johnson has had to spend political capital like it was going out of style to hang on to Cummings. So why?

1. Loyalty? This is the easiest explanation to dismiss. Johnson has betrayed wives, children, David Cameron, Theresa May, the ERG, the DUP, the new Tory voters in Red Wall seats, etc., etc. The only person to whom Johnson has ever exhibited loyalty is himself.

2. Cummings is so brilliant, he's indispensable? Not on the evidence of the last few weeks, surely? The government's response to coronavirus has been an error-strewn disaster. Plainly Johnson isn't much enamoured of work, and needs someone to do it on his behalf, but it's hard to believe Cummings is the only man known to the government capable of this.

3. Brexit? Do all roads lead here? Brexit has always been a house of cards. Even four years after the referendum (and decades after some to them started plotting), the Brexiters are still incapable of coming up with any credible alternative to EU membership. Brexit has always been a house of cards, and the Cummings card is right at the base. Does Johnson fear that removing it will bring the whole rotten edifice crashing down. (This might also explain why Cummings hasn't apologised. Maybe he and Johnson judged that any admission of fallibility, however small, could threaten Brexit.)

4. Does Cummings know too much? The question so courageously put to a Conservative MP by BBC interviewer Simon McCoy. Certainly if Johnson got on the wrong side of his 'adviser', there would be great danger that beans would be spilt - on Brexit, political funding, Russia (what was Cummings doing there for three years exactly?) or other things we as yet know nothing of. And it may not be only Johnson he knows too much about. What about all those other Tories who tumbled over each other in their haste to defend Cummings? 

My own bet is answer is 3 or 4, or possibly both.