Do you really think the people that supplied them with their software didn't do due diligence? The passport system I mentioned earlier was actually fixed in 1997 because we were already well aware of the possible problems of Y2K back then and we regarded that as pretty late (the system was scheduled to be decommissioned in 1998 but its life was extended due to is successor being a no show). Almost all third party software would have been patched well before 2000. If the Koreans and Italians appeared to do nothing I bet their IT people were still doing normal patching and upgrades and would have applied the Y2K patches without really being aware that they were.
But there are thousands of computers (mostly homes ones) that didn't have software updates etc in the time running up to 2000, and they just carried on working.
The issues were massively overhyped, and I'm not necessarily saying it was wrong to do so, because had the worse case scenario actually happened then there really would have been trouble. But it didn't, even in computers which had had no remedial action taken.
It is a bit like boarding over your windows with a hurricane on the way which might, or might not pass over you. In the end the hurricane didn't arrive and therefore those who didn't board over their windows (i.e. not taking any action) ended up with systems running fine, jus the same as those that did board over their windows (i.e. those that took action).
Again there were of course isolated situation where systems might have failed without action but the prevailing view that unless we took action all our computers (well PCs) would stop working on 1st Jan 2000 was flat out wrong.