Why would he want to "out" the manager? He already sussed out the situation for himself. He had nothing else to prove to anyone else. He was only there for a sh

Why would he want to "out" the manager? He already sussed out the situation for himself. He had nothing else to prove to anyone else. He was only there for a short time so probably hadn't made any meaningful friendships with other workers there anyway. The only thing the OP should have done differently, IMO, is made clear to his colleagues that he handed his notice and that he wasn't being sacked.