"he planned to join an academic institution"
Intel is most definitely not in any way an academic institution.
This guy is, at the very least, a liar and has clearly breached his non-disclosure agreement.
TSMC is perfectly right to pursue the matter in court, even if it is too late. Not that Intel is in a position to profit from any knowledge illegally gained at this point in time.
Personally, I hope this guy gets what he deserves : a long stint in prison.