As Boris and his acolytes (interminably) tell us, he was the only one who could have won that election victory as a Tory.
Now Boris has had to resign, essentially because his dyed-in-the-wool mendacity and innate lack of a moral sense have come - rightly - to be seen as deleterious to the common weal when possessed by a Prime Minister. (And also, perhaps, because people came to see the truth behind Tory lies.)
Put these two facts together. For Tories to gain power electorally they need a liar and a scoundrel as leader ... but it is a bad thing for the country when the Prime minister is a lying scoundrel.
In other words, any Tory leader, if capable of being elected as PM, will necessarily be a liar and a scoundrel, which will be a bad thing.
Is there a way out of this apparent conundrum? There is, of course.
Having lying scoundrels running the country is a bad thing that cannot be avoided if too many people vote Tory. So don't vote Tory. Ever.