Oh, it's far worse than that. No. 10 is nothing more than a step on the career ladder to these people these days, the ultimate aim being a cushty $$$$$-paying non-exec seat on several multinational boards, a speaking gig or two at a fancy uni, some well paid but meaningless UN synecure position and all the world travel, big dinners and pimms you could want, all aboard your private yatch.
Detest Thatcher as you should, there was always a sense she genuinely believed what she was doing was for the good of the country. The Camerons, Goves, Johnsons et al don't even seem to pretend any more. Sheer naked mercenaries.