I have read the original article as well as many pieces of additional context posted in this thread and yet still don't understand what is going on here.
Yes, the intern was actively behaving maliciously, but why? What did he stand to gain from breaking another team's training code? I don't buy that he went through all that effort and espionage simply to make his own work look better. An intern is only employed for 3 months, surely sabotaging another team's multi-year project is not the most efficient way to make your toy 3-month project look better in comparison.