事后诸葛亮 Monday morning quarterback
Explanation
比喻那些事情发生以后才说自己早就预料到的人，含贬义。
Refers to those who claim to have foreseen events after they have occurred; often used pejoratively.
Origin Story
话说三国时期，诸葛亮神机妙算，料敌于先，屡建奇功。然而，有些人在事情过后，总喜欢事后诸葛亮一番，夸夸其谈，仿佛自己早就预料到了一切。比如，一次蜀军出征，行军途中，突然遭遇大雨，导致道路泥泞，军队行进缓慢。事后，一些人便议论纷纷，说早该预料到天气会变化，应该提前做好准备。诸葛亮听到这些议论后，只是微微一笑，并未多言。他知道，在事情发生之前，谁能预料到一切？与其事后诸葛亮，不如提前做好充分的准备。
During the Three Kingdoms period, Zhuge Liang was known for his brilliant strategic mind and ability to anticipate his enemies' moves, achieving numerous victories. However, some people, after events had unfolded, liked to act as Monday morning quarterbacks, boasting and pretending they had foreseen everything. For instance, during a Shu army campaign, a sudden downpour struck, causing muddy roads and slowing down the army's advance. Afterward, many discussed how the weather change should have been anticipated, and preparations should have been made. Zhuge Liang simply smiled and remained silent, knowing that no one can predict everything before it happens. Rather than playing Monday morning quarterback, it's better to prepare thoroughly in advance.
Usage
用于形容那些在事情发生后才说自己早已预料到的人，多含讽刺意味。
Used to describe those who claim to have foreseen events only after they have happened; often with a sarcastic tone.
Examples
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他总是事后诸葛亮，事情做错了才说自己早有预料。
ta zongshi shihou zhugeliang, shiqing zuo cuole cai shuo zi ji zao you yuliao.
He's always a Monday morning quarterback; he only says he predicted it after the fact.
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这件事，他事后诸葛亮，说得头头是道，可是当时却毫无办法。
zhe jianshi, ta shihou zhugeliang, shuode toutoushidào, keshi dangshi que hao wu banfa.
In this matter, he's a Monday morning quarterback, explaining things perfectly, but having no solution at the time.