The kingdom passed to Boniface's son Demetrius, who was still a baby, so actual power was held by various minor nobles of Lombard origin.

These nobles, under the regent Oberto, began plotting to place William VI of Montferrat, Boniface's elder son, on the throne, and openly defied the Latin Emperor Henry of Flanders.

Henry of Flanders eventually defeated both, but after Michael's death in 1214, his brother and successor Theodore began anew the assault on the kingdom.

In 1224, just as Demetrius had become old enough to take power for himself, Theodore finally captured Thessalonica and the kingdom became part of the Despotate of Epirus.

[5] The kingdom was claimed by titular kings of the house of Montferrat until 1284 and also by the dukes of Burgundy; Baldwin II of Constantinople had promised the title to Hugh IV should he regain the Latin Empire.