The Lord put it into the mind of the Philistines and the Arabs who live near the Cushites to attack Jehoram.
References for 2 Chronicles 21:16
So they went to war against Judah and invaded it. They carried off all the possessions found in the king's palace and also his sons and wives; not a son was left to him except Jehoahaz, his youngest son.
References for 2 Chronicles 21:17
After all these things, the Lord afflicted him in his intestines with an incurable disease.
This continued day after day until two full years passed. Then his intestines came out because of his disease, and he died from severe illnesses. But his people did not hold a fire in his honor like the fire in honor of his fathers.
References for 2 Chronicles 21:19
Jehoram was 32 years old when he became king; he reigned eight years in Jerusalem. He died to no one's regret and was buried in the city of David but not in the tombs of the kings.
References for 2 Chronicles 21:20