Ben Simmons has played his last game with a Sixers jersey almost 100% sure. His value has come close to 0 for contenders teams but he's a great asset for rebuilding teams.
Pistons can rebuild around Simmons,Bey,Hayes and their picks, while Ben works on his shooting without the win-now pressure.
Sixers get a real PG who also has good defense. Grant was one of the best complementary pieces of the NBA in the bubble. This season he was a MIP candidate and he showed his evolution on the offensive side of the game. The Sixers would have a very fluid offense without losing a lot on defense.
Win-Win trade