Cracking software doesn't warrant hard prison sentences. That's a double negative for society.
This was back when programming was a highly skilled and difficult job that only a few could do, so cracking was even more harshly targeting people.
But someone, somewhere along the way did lose some amount of money.
The fact that the sentence was only 18 months reflects that, somewhat.
That is what copyright law fundamentally is.
We all learn from other people, just because I came up with an idea, I cannot tell other people "you're not allowed to use it". It violates other peoples natural right to autonomy to do so.
You're right, ideas are not protected by copyright.
Copyright only protects original works of authorship.
Nevertheless, my making argument against doing and condoning what this guy did is that, because of those type of actions today we have to deal with SaaS only software that is subscription based and stops working after the company folds (I can still use my Win16 copy of GetRight, thankyou very much).
We got into this sad state because of greed, from both sides of the counter.