Board Thread:Theories and Rumors/@comment-28313176-20180914131834/@comment-26537965-20180918191656

No. The FSM died centuries before Battle Between Brothers. Moreover, it has been said multiple times that he made Wu and Garmadon swear that they would protect the Golden Weapons. I think he just died of old age, I mean he already looked old, when Wu and Garmadon were children, so him dying of old age is the most likely cause.