Everyone loves the king. The king is so wonderful, we should all be more like the king. Blah blah blah. Bref has met the king, and quite frankly he was not impressed. Yes he makes a good speech, but he is dumb as a post, and Bref could take him with one hand behind his back.
Running in the general circle of crime, Bref and others began to formulate a plan to eliminate the king and install their own in his stead. Confidence has never been one of Bref's shortfalls. Needless to say they overlooked a few simple details and the night before the planned assassination and subsequent coup, him and his entire crew was arrested tried and convicted. Of course this might have happened because Bref and his crew are goblins.
Though Bref is perhaps the smartest goblin to ever have been born. By the age of 3 he had killed and eaten the chief and all his relatives. By 4 he had been ousted and then killed and eaten another goblin chieftan. That eventually got boring so why not kill and eat the human king?