The cliche is that it’s personal ambition that propels most politicians. Unfortunately, I think it’s true, at least for the biggest of them. What really drives most of them round the twist is not failing to get their policies enacted, but their ascent up the greasy pole being blocked.
For example, what really drove Anna Soubry mad was not the Brexit vote itself, but her being sacked from Cabinet. Same with George Osborne being removed as Chancellor. If he’d stayed as Treasurer, then, while he may not have liked the Brexit result, he wouldn’t have turned into the pantomine villain he now is. Boris Johnson has been all over the place since Gove withdrew his support for Boris’s leadership bid. David Milliband threw an epic wobbly and left the country when he didn’t win the Labour leadership. What drove Gordon Brown to despair was the thought that Tony Blair had reneged on his supposed promise to let Gordon take over after a while. Michael Gove has decided to remake himself as an environmentalist in order to overcome the perception (partly unfair, but partly earned) that’s he a sneaky little shit, so that he can rebuild his leadership aspirations.
This doesn’t apply so much to non-politicians. A. C. Grayling, for example, really has gone mad because of Brexit, and not because of any loss of promotion prospects. He has a purer form of madness. Not that that makes him any better — in fact, he’s a dangerous loony. Anna Soubry, on the other hand, would probably drop the hysterics instantly if she was given a job in Cabinet again.