之所以……是因为…… / ……的缘由，都要追溯到……
Reach for 之所以……是因为…… when you want to flip the usual cause-result order and put the result first, then explain why — 'the reason that X is because Y.' It's the move you make when the listener already knows what happened and you want to deliver the explanation as the punchline. The 缘由追溯到 variant pushes the search further back in time, tracing today's situation to a historical origin. Both belong to written and formal register; in speech, people just use 因为.
Structure
[SUBJECT] 之所以 [RESULT], 是因为 [REASON]
zhīsuǒyǐ... shì yīnwèi... / de yuányóu... yào zhuīsù dào...
How to Think About It
Normal 因为……所以…… runs cause → result. 之所以……是因为…… reverses that: result first, cause delivered as the reveal. The 之 is a literary placeholder ('the X-of-Y'), and 所以 here is a noun ('the reason'), not the conjunction 'so.' Mentally read 之所以 as 'the reason that this happened' — then the 是因为 that follows is the actual explanation. It's a rhetorical inversion, used when the writer wants suspense before the cause.
Examples
他之所以迟到，是因为路上堵车了。
Tā zhīsuǒyǐ chídào, shì yīnwèi lùshàng dǔchē le.
The reason he was late is that there was traffic.
我之所以选择这份工作，是因为它有挑战性。
Wǒ zhīsuǒyǐ xuǎnzé zhè fèn gōngzuò, shì yīnwèi tā yǒu tiǎozhànxìng.
The reason I chose this job is that it's challenging.
这场冲突的缘由，都要追溯到上个世纪。
Zhè chǎng chōngtū de yuányóu, dōu yào zhuīsù dào shàng gè shìjì.
The roots of this conflict all trace back to the last century.
Common Mistake
Learners drop 是 and write 之所以……因为…… because it looks redundant. In this construction 是 is required — it's the copula linking the result-noun (之所以...) to its explanation. Without 是, the sentence sounds incomplete.
他之所以成功，因为他很努力。
他之所以成功，是因为他很努力。
Don't Confuse With
因为……所以……
Standard cause → result order. Use 之所以……是因为…… only when you want the result first for emphasis.
由于……
Just states a cause neutrally at the start. 之所以……是因为…… is the inversion that puts the result first.
……的原因是……
Plainer version of the same inversion ('the reason for X is Y'). 之所以……是因为…… is more literary and rhetorical.
Practice
她____受欢迎，是因为她待人真诚。
Show answer
之所以
他之所以放弃，____因为压力太大了。
Show answer
是
Arrange: 是因为 / 之所以 / 学 / 我 / 中文 / 喜欢 / 中国文化
Show answer
我之所以学中文，是因为我喜欢中国文化。
Translate: The reason this restaurant is popular is that the food is authentic.
Show answer
这家餐厅之所以受欢迎，是因为菜很正宗。
Write one sentence using 之所以……是因为…… to explain a personal choice.
Show answer
我之所以搬到上海，是因为这里的工作机会更多。
Hear It in Real Episodes
This pattern appears in 1 Fluentide episode: