Partly because recruiting in women's basketball often happens very early in a player's career.
Stuelke committed to Iowa in May of 2019 (around 6 months before Clark did). She debuted for the team in November of 2022. Callie Levin committed in August of 2021 and won't debut until November of 2024.
Stuelke and Levin are somewhat unusual, but not dramatically so. Before Covid, Iowa often had its classes finalized months or even closer to a year before the players signed their national letters of intent.
So why didn't Coach Bluder bring in athletes to play with Clark? For Clark's class and the class after hers, the answer for many of them is that they likely committed before Clark did. Or before she started playing college games, at least.