I will have a go at answering your question Khandro !
After the disastrous choice of Major, Hague, IDS, and Howard, I think that the Tories knew that they had to have somebody who was electable, as yet another failed Leader would have been completely unacceptable.
Cameron won on a popular vote of 67%, so at last the Tories felt that they had indeed made the right choice. He was going to unite the Party, rather than antagonise it and divide it as the previous incumbents had done. He beat the Labour Party not once but twice, the last being less than 18 months ago, and was widely supported here on AB.
I have said this many times before, perhaps it won't matter if I say it again.
I am a committed Labour supporter, but it was obvious that if we were going to be defeated, Cameron stood the best chance of doing just that. He wasn't one of the usual "Nasty Party" lot, and he was, and still is, a basically decent chap, and
I for one am sorry to see him go.
Especially so now as we appear to have the beginning of one of the most rabid and regressive Tory regimes for a long time.