CFL short lifetime is mostly caused by high ballast temperature. And while the optimal position for an incandescent is vertical, base-up, lot of luminaires are build to fulfill this (to get longest bulb life and lumen maintenance), plus there is an enclosure diffusing light. But for CFL this is the deadliest combination - enclosing prevent good ventilation and base-up causes the ballast is in the hottest spot.
But the question was not why CFL's die too soon, but what cause the difference of the EOL failure mode between 120V and 230V versions.
My colleague put an hypothesis, then the reason is the voltage doubler in 120V versions: When transistors die by overheat (due to e.g. hard switching at lamp EOL), they short the DC bus after the rectifier. On 230V versions, as on the input is a bridge rectifier, this short causes very huge current from the mains, so the fuse (or CB) trip and disconnect the power before some bigger component overheat to cause fire. But when doubler used, the short current is limited by doubler's capacitors impedance, so the current is low to trip the fusing, but large to gradually overheat them and set the fire.
But this does explain only, when the smoking does originate from capacitors, not the tube.
So still, how to explain
this ? Where the severely overheated component are the tube ends and not capacitors in the doubler? This failure mode seems to be quite common in 120V area (repeat's many times on LG), but i have never seen any in 230V area. In Europe we have only hard-shorts (and on better quality pieces the internal fuse react quicker, the CB trip)