Well, you came close but, ultimately, you elide the real problem: Boris Johnson is supremely competent at campaigning and getting elected. Of course Johnson is going to be incompetent at the job: he’s only ever ever exerted himself in trying to get elected. Once elected he’s too busy looking ahead to the next thing to perform adequately on the job. This should scare you incontinent.

The problem isn’t Johnson’s incompetence; it’s that campaigning for the job requires different, perhaps contradictory, skills to those skills necessary to, you know, actually do the job. We, the people, aided and abetted by an indefatigable media — a media addicted to conflict and allergic to nuance — choose the person on terms and conditions that are largely antithetical to the actual job requirements…

Johnson, and Trump — and Ronald Reagan, Bill Clinton, George W. Bush and, sadly, Barack Obama — are, or were, quite adept at sucking up all media oxygen, starving all others… they spent their lives perfecting this strategy and it leaves them alone and unable to make actual and real life decisions. Of course they are incompetent: it’s baked into the system.