According to Jason Lloyd of The Athletic, Drummond told the Cavs he would leave after this season if Beilein returned. Drummond has a $28 million option for 2020-21.
Beilein has drawn the ire of his players at several points this season, so it's not as if Drummond would have been the sole reason for his departure. Or even the main one. But it's safe to say Drummond recognized the disconnect between the coach and the team in two shorts weeks since the trade.
The most visible of Beilein's dissenters was Kevin Love, whose agent Jeff Schwartz also represents Drummond. Love is under contract with Cleveland through 2022-23.
Drummond, 26, reportedly plans to opt in next season, after indicating last summer he intended to test free agency. The Cavs are in last place in the East.