Henry 'Bolingbroke' was the son of John of Gaunt, Duke of Lancaster. Bolingbroke didn't make it a secret that he thought Richard II was a lousy king and unfit to rule. Richard banished him, and then stole his inheritance (and his title) when Gaunt died. Henry returned to claim his estates, saying that he just wanted back what was rightfully his. But he quite quickly changed his story -- he wanted to be king. He deposed Richard II and became Henry IV.