in those days computer crimes weren't punished that harshly. I'm surprised it was that severe, in fact, it sounds like there must have been some heavy hitters on the prosecution side.

I think the story is that this was one of the first ever prosecutions under the CFAA and they quickly realized that the fact it had taken down so many systems was an accident (there was a bug in the replication code). The prosecution was mainly to establish precedent in an emerging field of law and technology.