How can a person answer a question without entering the community? I don't understand. Maybe the time in picture doesn't mean the answering time.
The user's account was (probably) deleted at one point. "Probably" because records going that far back are not always consistent or available, so I'm guessing on that part.
The post ownership was reassigned to the new profile a couple years ago. We don't do this often as profile deletion is serious and shouldn't be taken lightly, and verifying post ownership after deletions can be tricky. Nevertheless, that's the explanation here.