The natural assumption about any married guy is that he got married for the usual set of reasons, so as I was with President Obama, I'm always a little surprised to find out that some married guy is gay.
There are women who enter into a marriage of mutual convenience, knowing that that's what they're getting into, and understanding that their role is to maintain the appearance of a normal marriage. What such a woman gets in return is usually a certain amount of financial security. And given that a woman willing to enter into such a marriage may well be gay herself, she may also benefit from the false front.
But there are probably a lot of marriages where a woman is fooled into marrying a gay guy without being aware of his proclivities. I think this was much more common in the past, back when homosexuality actually was the love that didn't dare speak its name, and there was more pressure on men to get married and produce a family. It was probably also more common because of the pressure for a woman to "save herself" for marriage.
I've known of a few marriages like this, and they always struck me as tremendously unfair to the woman -- especially back when divorce was regarded as a larger stigma. A gay guy, by essentially tricking a woman into marriage without letting on that he is gay, is effectively consigning her to a marriage without sex.
It's not that regular sex lasts for that many years anyway; people do tire of each other, and after ten years most marriages are nothing more than an accumulation of petty resentments. But this kind of dishonesty still seems tremendously selfish.
I don't think the Obama marriage was like this; my guess is that Michelle knew perfectly well what she was getting into, and there was no subterfuge on Barack's part.
On the other hand, it was dishonest for him to pretend to be a moderate when he was in fact a radical.
Michelle may be satisfied with her arrangement, but the country itself is currently in a very bad marriage.
(Time for a divorce.)