This is pure slander
The company can avoid this if they only care to maintain the documentation / wiki left behind by said person
When they failed to do even just basic proper operations, it's their own fault.
I'm a business owner and a consultant, and I too charge more for these kind of asshole clients, because of the extra stress.
But nowadays I just try to avoid them, it's just too damaging for your own sanity. Their kind of stupidity, self-entitlement, and ignorance is on a completely different level.