だと気づいた

realized that it was

→ だ
phrase Rare #30,346
realized that it was Follows a statement or description that someone came to realize. The subject is usually understood from context.
JA: 彼が正しいのだと気づいた。
EN: I realized that he was right.

父と船が姿を消してから、父の船の名を口にしたのはこれが初めてだと気づいた。

I realized this was the first time I’d said the name of my father’s ship since he and the ship disappeared.

突然仮面の後ろの顔が君だと気づいたのだ

Suddenly, I realized that you were the face behind the mask.

— 28年後... 白骨の神殿 (2026)

注文する前に、私は自分の名を人に覚えていてほしくないのだと気づいた。

Before placing my order, I realized I didn’t want people to remember my name.

彼女は私だと気づいた様子はなかった。

She didn’t seem to realize it was me.