It doesn't make a lot of sense to me. People at the time must have known that fires in cities were extremely dangerous because they could spread over a great area. It's logical that insurers would want to work together to prevent all fires, purely out of self-interest to protect their insured properties, and then sue the pants off negligent and/or uninsured property owners after each near-miss.
The paper in TFA says as much, but it's weird to me that people would uncritically accept the proposed narrative in the first place.