怪不得

HSK 7-9

guàibude

not surprising that; here's why (explanation a posteriori)

so that's why!

怪不得你没来参加聚会。

guàibude nǐ méi lái cānjiā huìjí

There's nothing surprising about your not coming to the party.

怪不得他总是迟到。

guàibude tā zěnme zhōng dào cháo

Nothing surprising that he's always late.