That's not new. This will be the fifth time in the last 50 years that a new leader has been chosen by the party at the time forming the government and hence become PM: the others have been Callaghan, Major, Brown and May herself (nicely symmetrically, two from each party).
Jeremy
But it's different this time: we are inevitably about elect a suicide jockey who will, for dogmatic party purposes, attempt to lead the country over the cliff. It is only due to Parliament, as a whole, having had - so far - enough intelligence to agree to disagree on anything but leading the country into the the worst deal possible: no deal. Why? Because they know the reality as distinct from the lies. I voted Tory every time I had the opportunity; never again. From the way they treated Thatcher onwards they have shown themselves as ruthless political careerists with not a saving grace in sight.
Sadly, the rest of the breed appears to be no better.
Perhaps we do end up having the politicians we deserve.