King Prusias was an ill-favoured man, and though possessed of fair reasoning power, was but half a man as regards his appearance, and had no more military capacity than a woman; for not only was he a coward, but he was incapable of putting up with hardship, and, to put it shortly, he was effeminate in body and mind through his whole life, a defect that no one, and least of all Bithynians, like to see in a king.
In addition to this he was most incontinent in satisfying his sensual appetites; he was entirely a stranger to literature, philosophy, and all such studies, and generally speaking had no notion whatever of what goodness and beauty are, but lived by day and night the barbarous life of a Sardanapallus.
So that all his subjects, the moment they saw the least chance of success, became irrevocably resolved not only to throw off allegiance to the king, but to exact punishment from him.
Walbank Commentary