Or: He took one look at the baby realized it didn't resemble him and said “Adios”!
From the fact of them getting divorced after a sufficient period of time passed by, seems to indicate that it was a marriage in name only. In other words, he knew it wasn’t his son because he was getting married only for appearances. There was probably some incentive for him (but I wouldn’t know what that would be). I guess there was the additional prestige for having another wife.
She probably already knew he had another wife and the reason why they had to go back to Kenya (so he wouldn’t face bigamy charges). I doubt that was a problem to her. She just wanted a “name” to have to say she was married and pretend that this guy was the father. The father was probably this other guy who was married and had sex with her (and his wife) as part of his sex escapades (he wrote about some of this in a book he wrote; can’t remember his name right now). He doesn’t describe her by name, but describes a situation that sure sounds like her. That guy is probably Obama’s father (but it just doesn’t say that on the birth certificate... LOL...).
She was so messed up as to what she was doing that there’s no telling who is Obama’s father and what his mother was doing.