Insurance carriers don't pay claims if the insured is the arsonist and burns their own property. If the claim does involve arson by someone other than the insured, the entire process will get slowed down until the C/O is completed and it is determined that the named insured did not cause the fire. The named insured has to be completely out as the arsonist. That solve your challenge? I just finished six hours of depositions on a seven year old fire that only recently had the named insured taken out of the picture as the arsonist. It will be a 12 million dollar case when its done.
Negligence comes in if the insured does not maintain the property or asset and lets it deteriorate steadly over time. More true of a wood trestle than a steel bridge. Negligence also comes into play if the insured does not act to mitigate the damages, ie try to put the fire out or plug the leak.