OOM issues often don't _really_ cause a crash unless you are running with real memory only. Usually long before you are out of total memory you are using so much virtual memory that the kernel is thrashing IO to try keep up with all the page faults. At this point the machine hasn't crashed, but from the outside it might as well have because it can't respond to anything new, even diagnostic intervention, in a timely fashion.

CPU overloading, without memory starvation, can have a similar effect, though that doesn't tend to fall off the same efficiency wall as when IO is the issue (unless something has literally kicked off a fork bomb) because of the orders of magnitude differences in latency and work throughput.