hindsight is 20-20 (even for a fool)
Rare expression meaning that even a fool can be wise after the event. Similar to 下種の後知恵.
See also: 下衆の後知恵
There is a proverb: 'Even a fool has hindsight.'
Kanji spelling of this rare expression; the reading こけのあとじあん is not obvious from the kanji.
Mixed kana-kanji spelling that clarifies the reading of 虚仮.
The expression combines 虚仮 (fool) with 後思案 (hindsight). The exact origin is uncertain, but it is a traditional proverb.