The closing ranks without even any expression of doubt is revealing.
Yes - very revealing.
The Conservatives have a massive majority, so politically they can withstand a lot. Even if he didn't leave government, if Cummings had offered an apology and admitted that, under stress, he had not done what the government had asked everyone else to do, there would still be a sense that the rules are important. It would be unpopular, but what can anyone do?
However, instead, the government have decided to protect Cummings by trashing the rules.