Why would a boy decide to date a shallow girl after having dated only top intelligent girls his whole life?

I have this friend who only ever dated super intelligent, pretty (and also rich) girls. They really were the cream of the crop, full of important awards and with stellar curricula, and he gave a lot of importance to their education careers etc, to the point he always made me feel like shit about myself.
The moment he turned 30 he dumped his girlfriend and started dating a good to nothing girl whose big passions are fashion and partying and who works as a secretary in the fashion industry… she really is a shallow person and even if she’s rich herself, she really gives the impression of someone who just wants a wealthy husband to maintain her.
I believe he made this (desolating) choice because he thinks a stupid girl will be an easier wife. But I wander how he can even think to spend his life and have a family with someone who is that hugely less intelligent and ambitious than any girl he ever dated. Can you date someone you consider stupid?
Why would a boy decide to date a shallow girl after having dated only top intelligent girls his whole life?
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