My understanding is that that's decomposition followed by combustion of the decomposition products (free radicals). Looking at the electron density around the

My understanding is that that's decomposition followed by combustion of the decomposition products (free radicals). Looking at the electron density around the C-C bonds gives some hint as to why they're stronger than they look. In general "backbone" single C-C bonds are pretty tough; there's a reason double bonds are always the attack sites, if they exist.