I didn't get the impression the person in question burglarized the Kingdom Hall. It sounds more like this person just walked in and took the documents. It doesn't sound like the local elders found the front door of the Kingdom Hall busted open and the file cabinet pried open as well. It sounds more like an elder was just going through files and noticed them missing.
This adds clarity to the situation. As the person was a member of the corporation, with voting rights (e.g an elder with a key to the cabinet) this explains why watchtower couldn’t legally go after him, but subsequently removed him from the corporation for bringing that corporation into disrepute.
If this scenario is correct, it sounds as though the theft was more a protest, in that he deliberately wanted to be found out. Why steal the physical files. It would of been more concealing to have photographed the documents and returned them to the cabinet. Then when they turned up on the internet, just deny it. He would of been a fool to have thought that the other elders wouldn’t of noticed such important files missing.
If the objective was to be caught red handled, then why appeal his removal from the corporation (e.g disfellowshipping). Unless the purpose was just to stoke the hornets nest even more.