Psychology would say this is confidence, as others have already mentioned. You can’t possibly track all the minute changes to your posture, facial expressions and attitude to tell what exactly is causing the increase in mate-ability.
But rest assured, it’s the sum of those mental and physical adjustments your body makes that brings them around.
It only works for some folks. For instance, there is no amount of testosterone or inches of girth (in any respect) that I can bring to the table for a woman to believe I am a suitable man for her needs, simply because the superficial types (and that is probably a majority of women) cannot reconcile in the same sentence the idea of feeling protected by a man who is of humble stature.
That said, what does overcome all that is money and power, lol. Women... they are so helpless without a protector, be it a strong man or the government, they must have one.
Fortunately, I have as a wife, one of the few decent ones left that measures a man by his character and not by his height.