The problem with Rory's argument is that we had already experienced the hyper-managerial eficiency of May and her dynamic duo.
Which was not an insignificant accomplishment, and not an insignificant factor in her own leadership victory. People were genuinely quite impressed that she had survived and thrived in the home office for five+ years, a dept that is famously branded "the death of political ambition". Her tenure in the Home Office faced a number of difficult social problems, that almost always result in unpopular policy the Minister then has to own.
But managerial efficiency - being on top of the detail - was not a solution to the problem of brexit.
The problem was simply too massive for any one person to be 'on top of', and the divides too large for a mere manager to paper over.
This is why you have Chairman, to manage the social temperature of the 'organisation', and for better or worse that is what people hoped boris might achieve in the ruins of May's failure.
And, as an explicitly 'not a detail person' he had built a reputation in london as an effective delegator who brought in good people and gave their head to get on and do what he wanted them to do.
None of the above speaks to boris's wider suitability for the job of prime-minister, but the idea it just needed a "focus on detail" manager has been tested to destruction.
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