I sort of do understand this phenomenon and sort of don't. On the "do" side, apparently testosterone levels rise with one's power (amazing I have any at all). This is in both men and women, and in both sexes high testosterone levels create greater desire for sex. Testosterone levels also probably raise the level risk taking. This, unfortunately, reinforces the general arrogance of power. Hence, we have politicians indulging in all sorts of really risky sexual behavior, not only Clinton playing around with Monica Lewinsky, but as well presidential hopeful Gary Hart's 1987 escapade on the yacht appropriately named "Monkey Business."
On the "don't" side, I find it hard to understand the arrogance - even with the testosterone factor - of televangelists and Christian apologists like D'Souza that makes them think they can preach sexual morality to the rest of us, while they themselves violate it.