It is called "regression towards the mean" (https://en.wikipedia.org/wiki/Regression_toward_the_mean). If someone is at a particular extreme, and the trait is hereditary in less than 100% (biologically or cultural), it is likely that their offsprings will be less extreme.

On the contrary - I find it sad that more intelligent and more accomplished people have fewer offsprings on average than others. While the process is not surprising socially, either there is no hereditary factors in intellectual abilities at all (which does not hold water), or step by step, we decline. Let's hope that technological augments to our mental capabilities develop faster than the biological process.

Once I compared the trajectory to "Idiocracy" (from 2006). Yet, a friend said it is an optimistic movie - since they still choose the smartest person as their president.