[Belegorn]

Reading some of the other things besides the Silmarillion regarding Fëanor it appears to me like a fire no longer contained, and out of control. In one version his mom lives while he grows up and she restrains him, but in any case, it would appear his mother name, "spirit of fire", blends into his actions during the rebellion. I do think the 2nd marriage of his father was really the thing that got things going. It seems the Valar themselves were worried about this. In the end some small part may be attributed to Melkor's influence in Arda, Morgoth's Ring.