if indeed the account is hacked, the main owner will automatically create a topic in Meta to follow up on that account, of course with valid evidence, in this case there is not much that can be concluded, except: based on the presumption of changing hands, being sold or otherwise.
Sure, owner would come here and said something about being hacked, but only if he was also active on the forum at the time (a lot of hacked accounts are used for spreading malware and the real owners extremely rarely show up). In this case account woke up 4 and a half years later so I doubt that real owner would notice something happening. Btw there's no real evidence here that account has been hacked but imho account changed hands somewhere during 2017.