Interesting that everything else was intact and, looking at the wire, it seems indeed original. If you have bought this used, there is a chance it might have been replaced before without your knowledge. Well, that or the capacitor itself was a bad part mounted in factory where a minute corrosion was present and became noticeable only after decades. At this point all is a guess.
Regarding the cracked capacitor, I also have seen this happen when corrosion in the leads is severe: the leads become so corroded that it weakened the ceramic and it cracked at the slightest touch. But in the cases I have seen, the corrosion was clearly an outside job (humidity, electrolytes, etc.)
Well, it is good that you found the issue before extensive PCB damage happened. These meters are sturdy as they come.