How does a detached garage decrease fire risk? It’s just another room in the building, as long as you aren’t parking an EV in there...
People keep gas cans and things in there.
No EV in this home, still driving a truck with roll down windows and the best anti-theft device on the market... a clutch!
Fires that start in a garage are hotter because of the flammable items stored inside - gas, paint cans, cleaning fluids, etc. When those fires spread to the home they cause greater damage than say a kitchen fire contained to the stove area. Replacing a kitchen is cheaper than replacing an entire home. A detached garage mitigates that as long as there is no covered walkway connecting the garage to the home. It is all about the lowest payout when it comes to property damage.