The Dallas Mavericks traded for Kostas Antetokounmpo on draft night 2018. The deal involved three second round picks. It saw the Mavs land both Kostas and Ray Spalding.
From the beginning, Antetokoumpo was meant to be a developmental player for the Mavericks. He had a slim chance of seeing the NBA court during his rookie season. After seeing no real improvement in 2019 summer league play, it was time for the Mavs to end the experiment.
The NBA draft is a gamble, especially in the second round. So this is not a massive loss for the Mavericks unless Kostas is a reason for recruitment.