It makes understanding people easier - much easier, in fact - but it doesn’t necessarily help you use that understanding any better.
Firstly, as others have observed, it makes it hard to relate to others when the majority of people you meet seem to have the intellect of a child - I don’t mean this unkindly, rather more that one ends up looking at most folks as making grievous and avoidable errors incessantly, and almost as overgrown children. You want to help, but you can’t, because nobody likes being patronised or made to feel inferior, but if you don’t help, they resent you for not having helped. It isn’t intractable, but it’s most readily avoided by avoiding interaction in the first place.
Secondly, intimidation. Ties back to making people feel inferior, and generally stymies social interactions. It’s tough, even in a marriage, as they either know you’re playing dumb, or feel like you’re beating them over the head with your intellect. Either way you end up hurting their self worth every time you notice something or think of something and unwisely decide to share it.
Thirdly, overshoot. I tend to assign far more intelligence and cunning to others than there is, and resultabtly second, third, fourth guess their mind-state, as it’s hard to comprehend the disappointingly facile motives behind behaviour.
Finally, expectations. Once you let on that you can solve the intractable while half-asleep, you’re expected to do it day in, day out, and find that the world beats a path to your door with their petitions and demands, which feeds more than a degree of misanthropy.
I’ve met maybe three people in my life who I’ve felt on a level with, and one of them is my brother.