Apparently he was assassinated because of his connection with the Korean Unification Church . His grandfather i think? helped push that cult in Japan because of the CIA's orders and that cult bankrupted a lot of Japanese people and the cult had the belief that Japan owes Korea money and women because of Japan's sins,

I don't believe Shinzo Abe believed any of this though considering he opposes many of the ww2 accusations against Japan since one of his grandparents was also branded a "war criminal" and obviously he wouldn't like that. . i believe he had his hands tied behind is back when he promoted that cult.