If it is a disaster for bitcoin then I think it could be just a catastrophic loss of internet or catastrophic global blackout, if we want to make a bitcoin purchase, sale or exchange transaction then it will not be possible if no internet and no electricity. I hope this is just suppose.
If that happens I think its almost the end of the world I know that some companies dont blackout because they need their operation running 24/7 so that goes to show it is also possible to not blackout in servers, etc.