Cruise lines, like nearly every other segment of industry and commerce, have become utterly dependent on computer systems to automate and run things. And as a result, things grew so big that it became impossible to run them manually.
The IT systems are as necessary now, at that huge scale, as wings on an aircraft. It's a terribly dependent situation, and one which was predicted long ago. They could have avoided it, but greed rules.
They made their bed, now they must keep it from catching fire over and over.
(And I, too, am an IT guy.)