Why is Michelangelo's David not so well endowed ?

Why is Michelangelo's David not so well endowed?

There are basically two explanations.

First, the ideal of beauty in ancient times.
In ancient Greece, a large penis was considered a sign of stupidity, lust, and animalism. The ideal Greek man was intelligent, rational, and authoritative. For this reason, ancient Greek statues often depicted men with small genitals. The Romans adopted this detail. Since the Renaissance refers back to antiquity, David's penis is correspondingly small.
The other reason is related to David's tension.
The statue shows David just before his fight against the giant Goliath. The sling is already on his shoulder. Despite his relaxed posture, signs of tension are clearly visible in the details. In such a situation of fear and danger, the genitals also shrink. Michelangelo was a master sculptor and had excellent knowledge of anatomy. This is also evident when looking more closely at the details of the statue of David.

The right hand is relaxed on the side, but the fingers are slightly contracted, the forearm muscles are tense and the veins are clearly visible. Even the distant gaze and wrinkles on the forehead and between the eyebrows reflect fear, as do the tight lips. Tension is also visible in the tendons of the neck. David's underdeveloped genitals could therefore have both biological and aesthetic reasons. David is naked, he's scared, he's under stress: all factors that can reduce penis size. Michelangelo was certainly aware of this.