To be decent at chess also requires an ability to methodically think through the implications of each possible move.
Although this might seem like stating the obvious, I don't think it necessarily can be taken for granted that everyone is equally strong at this kind of thinking.
Maybe it's just due to impatience, or maybe there are actually differences in people's ability to keep these details straight so that they don't lose track of what they have and haven't considered, or maybe it's something else. Even if it's just impatience, conquering that impatience might be one of the factors in intelligence. And there might even be differences in brains (perhaps anxiety) that could affect how much patience one has for this kind of mental effort.
Although this might seem like stating the obvious, I don't think it necessarily can be taken for granted that everyone is equally strong at this kind of thinking.
Maybe it's just due to impatience, or maybe there are actually differences in people's ability to keep these details straight so that they don't lose track of what they have and haven't considered, or maybe it's something else. Even if it's just impatience, conquering that impatience might be one of the factors in intelligence. And there might even be differences in brains (perhaps anxiety) that could affect how much patience one has for this kind of mental effort.