不明就里

不明就裡
bùmíngjiùlǐ
  1. not to understand the situation
  2. unaware of the ins and outs

CEDICT

to not know the inside story; to be unfamiliar with the details of the situation

Wiktionary

不清楚、不了解事件的内情。

重編國語辭典

Entry Composition

1 不明 bùmíng
  1. not clear
  2. unknown
  3. to fail to understand
2 就里 jiùlǐ inside story