expression
hindsight is 20-20 (even for a fool); an afterwit is everybody's wit
Proverb meaning that even a foolish person can seem wise after the fact. Used to criticize someone who claims they knew something all along only after it happened.
失敗してから「やっぱりそうだと思った」と言うのは、下衆の後知恵だ。
Saying 'I knew it all along' after a failure is just hindsight being 20-20.
His advice is always after-the-fact wisdom and never helpful.