very likely a reload that got over charged with powder…
although from time to time there have been factory loads that somehow got overcharged…
but that is very rare…
or someone used the wrong powder to charge the round…
modern firearms are well made but they can be destroyed with improper ammo…
As I posted before - a b & w video featuring Bill Jordan years ago, which featured his trick-shooting with ping-pong balls and wax bullets - ended with a short interview, where he was asked this same question. Back then, pistols had a reputation for unreliability, not reaching the level they’re at today. Jordan replied that if a DA revolver misfired, all you had to do was pull the trigger again - the time it took to re-rack a pistol to clear a misfire cost you valuable time, which could prove fatal. FYI - Jordan helped to design S & W’s Model 19, .357 Combat Magnum, which debuted in 1957 - I was 7 at the time.
A round being in the cylinder aligned with the barrel is not the round that detonates when the trigger is pulled. That has little to do with anything. Semi -autos are mostly easier to conceal. Still, personally, I prefer to carry a revolver, mostly, for the last 50 years. I’ve had alota experience with semi-autos,(alota years in the military, some combat), .45 & 9mm. Civilian life, various pistols from 22LR to.45s. also Revolvers. A few real civilian self-defense gunfights, no long guns involved. I was also robbed once at gunpoint, early in my 20s. Twice, people agitated at me, pulled a gun on me at a time I was not armed. It was very uncomfortable, especially the guy with a shotgun.