Anything as equiptment threatening as that is on topic.
First as Erik said all live line terminals should have baricades for safety.
If you examine a line powered smps you will see a clear separation zone between the power input and the low voltage side. You should employ the same system in all line powered equiptment. Line side shoukd be separated from low voltage side by distance and a physical barrier.
The separation and barrier will if properly done reduce emi issues as well.
Anyone servicing or maintaining equiptment can and indeed will have an oops day, but it need not be this bad.
Glad nobody was injured beyond your pride.

The problem with these failures is that unlike spikes or esd these faults expose the electronics to sustained high power levels and will destroy shunt protection devices often before the line fuse or breaker has a chance to act. The best protection is prevention Good luck Terry