This is a tricky situation.
By all accounts, the first version of the answer - which was accepted - had some pretty incorrect statements in it. (This is why you don't accept answers within a day, people!) It should have, accordingly, been downvoted.
Andras's edit was definitely an improvement. But it was also an edit that was too major, outright replacing a significant portion of the original answer. In this case, Andras should probably not have edited it this way and it probably shouldn't have been approved: Andras should have downvoted, and posted their own answer.
In this circumstance though? Probably just leave it as is and avoid making this situation messier. I'll leave a comment on the answer letting Andras know about this.
On this note, though: sometimes people perform a too-major edit on a bad (but accepted) answer, and explain they wouldn't normally have done it, but it was the accepted answer, and that one should be correct, right?
Don't do this. Accepted answers don't get special treatment. If it's wrong or a bad answer, downvote it, then post your own, better answer. If the answer with a tick beside it has a low or negative score, and it's followed by one with a much better score, they'll get which one's the better answer.