Adding onto what everyone else said, he was drafted in the same year they took Trae Young. They gave free reign to both guys to do whatever they wanted, but Huerter just never took advantage of that opportunity. He didn't really progress the way they were hoping for, and he hasn't really developed much since his rookie year.
He's still young, but after very little growth in 4 years, the player we see is probably he player we'll get. Maybe + a coupe ppg.
Their salary situation made him very expendable. However, it wasn't a DDV situation where they just gave him away for free. Atlanta got a really good return for him. A Kings 1st round pick could be anywhere from pick 12-19 (assuming it conveys). They didn't see Huerter as their long-term SG, and at the same time, they also thought Bogdan was better.