1950: 6,405 fire deaths / 150,000,000 US pop = 0.00427%
2022: 3,490 fire deaths / 335,000,000 US pop = 0.00104%
a) better electrical wiring and circuit provisioning. Overloaded outlets or circuits were more common in the 1950s. Fuses could also be tampered with more easily than circuit breakers.
b) Matches everywhere. You had matches in the kitchen for lighting the stove, and around the house for lighting cigarettes. "Kids playing with matches" was a common cause of fires. You don't hear about that nearly as much today.
In 1950 around 50% of adult males smoked, these days it is closer to 15%
"Smoking in bed" was such a common cause of fires that even in elementary school we were taught "never smoke in bed."
Basically everything is soaked in flame retardant: your insulation, your wiring, your furniture, your appliances.
Heater technology is way safer now. Central heat is a lot more prevalent, and space heaters are a lot less likely to start a fire.
I'd also add to your wiring point: electrical appliances are way safer and way less hot.
A counter-argument though is the prevalence of lithium-ion batteries. I do wonder if a spike in fires is coming--though I would've expected it by now.
Arguably came and left. In the early 00s battery pack explosions in cell phones wasn't a super rare event. Now Li batteries are a lot safer with better protections to keep fires from starting. Additionally, the biggest batteries someone is likely to setup for their homes are LFPs which are quiet resistant to starting fires. If sodium batteries are successful they'd go even further in being a non-issue.
Similarly the murder rate is a more accurate than other crime rates. Burglaries, muggings and assaults are often not reported to police whereas violent deaths almost always are.
Gred's post however strongly implies that the only outcome worth considering is death. That might be true for them, but I'm not sure if that applies broadly.
Speaking from experience, losing your house to a fire is traumatic, expensive, and you lose things that can't be replaced. Even when there are no deaths.
Like, a big reason for fires in the 50s was paper covered and underspeced wiring.
Safe wiring simply uses plastic instead of paper.