였으니

since it was, because it was

→ 이다

였 Past tense + 으니 Because/since

auxiliary · past tense Rare #28,120

since it was, because it was The past-tense form of 이다 followed by -으니, giving a reason or background for what follows.

KO: 그는 의사였으니 건강에 대해 잘 알았어요.

EN: Since he was a doctor, he knew a lot about health.

Conjugation of 이다

It was an accident, so there's nothing we can do.

— 미스터 헐리웃 (2000)