It was not your mistake. Your frustration and confusion are understandable. Prepare yourself for the possibility of never obtaining satisfactory answers or reaching a closure that feels satisfying. But treat the situation as dodging a bullet. Something like this would feel far more hurtful if it happened further along in your relationship.

Regarding his doing fine, as indicated by social network posts, this might be true or a façade he presents; again, prepare for the possibility of never knowing the truth.