Their parents likely spent effort (in assortive mating, proper nutrition, early stimulative interactions, etc.)

You could call placing 99 green balls and 1 red ball into a bin and picking out 2 green balls a “lottery”, I suppose.

How is "being smart" a genetic lottery? Are you serious? That brings up all sorts of implications with race and whatnot. "Being smart" is often a proxy for the things the GP mentions: strong stable family, access to good schooling, and a sprinkle of luck.

Heritability of IQ is >50%, and IQ is a good measure of smartness.

The previous comment's argument appears to be that heritability of "being smart" is not strictly limited to genetic factors, that measures of "smartness" such as an IQ score also measure other factors that are not strictly related to genetics

Heritability and genetic factors are overlapping but distinct things - for example, socioeconomic status influences many aspects, is hereditary but not genetic.

Heritability is in fact entirely genetic. It is estimated by comparing monozygotic twins with dizygotic twins.