Okay, something the younger ones amongst you might not he conscious of. For wonkish political nerds in the UK of a certain age (I think roughly ranging from older millennials in their late-30s to the Cameron/Osborne/Clegg/Miliband generation in their mid-50s) and regardless of their political party affiliation (I've found this equally true of Labour, Conservatives and Liberal Democrats), probably the piece of popular culture that has most influenced how they think about the 'romance' of politics is Aaron Sorkin's The West Wing, which aired in the late 1990s and early 2000s. It's brilliant TV and anyone who hasn't seen it should watch it.
Sunak is a very wonkish political nerd in that age bracket. He's also someone with a particular relationship and affiliation with the United States. I would guess he is almost certainly a West Wing fan.
I've been thinking about The West Wing lately because of an article Sorkin wrote for the NYT, comparing the scenario around Biden and the 'will he/won't he' be the Democratic presidential candidate to his season two finale when President Bartlet - who has been concealing from the public that he suffered from multiple scelerosis - disclosed his illness and then, under huge political pressure not to stand for re-election due to his condition, dramatically changed his mind at the last minute and revealed he would.
The ending scene of Bartlet heading to the press conference to the soundtrack of Dire Straits is a top 5 moment for any fan of the series. It's tipping it down with rain and Bartlet shows up, drenched, walks out in front of the world's media like a heroic figure battling the very elements themselves, and commences his re-election campaign.
I hadn't made the link before but, now that I think about, I am certain that is exactly how Sunak and his advisors thought he was going to look on the TV news that night! We all spent all that time joking about how this man who claimed to have 'a plan' couldn't even rustle up an umbrella in a rainstorm - but the lack of an umbrella was deliberate! Oh dear god, the poor man thought that was his Jed Bartlet moment!
It's entirely plausible. I'm positive they have the ego and lack of perception for it but I think it's simpler than that - they're just stupid.