“之所以…是因为…”
HSK 5
之所以 + A，是因为 + B
强调原因（因果倒装）。
Examples
我之所以喜欢它，是因为它简单实用。Wǒ zhī suǒyǐ xǐhuan tā, shì yīnwèi tā jiǎndān shíyòng.
The reason I like it is that it's simple and useful.
他之所以成功，是因为他坚持。Tā zhī suǒyǐ chénggōng, shì yīnwèi tā jiānchí.
The reason he succeeds is that he persists.
