In 2015 a powerful book* Dr Frances Flannery, a scholar at James Madison University in Washington, analysed the nature of apocalyptic terrorism. The author looks at case studies within the environmental movement, in Japan, amongst militant Christian militia groups in the USA, and in Islam.
For me the key finding was that whereas fundamentalist attitudes with an apocalyptic, imminent end of the world approach, in some groups might lead to psychological harm or isolation for their members, it was the sense of who was responsible for bringing in the rule of God that made the difference. If the answer was that God was responsible, the group was unlikely to be violent. Once they felt that they had a responsibility to do God’s work in the place of God, then extreme violence was inevitable.
In other words the issue is theological. What is the understanding of God that we have in terms of responsibility for a righteous society.
Read it all (my emphasis).