It's because he can't reconcile being a party leader with being a Christian. He said: "The consequences of the focus on my faith is that I have found myself torn between living as a faithful Christian and serving as a political leader. A better, wiser person may have been able to deal with this more successfully, to remain faithful to Christ while leading a political party in the current environment. To be a leader, particularly of a progressive Liberal party in 2017 and to live as a committed Christian and to hold faithful to the Bible's teaching has felt impossible for me."
Does the attack when a man drove a bus into worshippers at Finsbury Park mosque count as terrorism?