のは当然

it is only natural that

→ の
phrase Common #7,176
it is only natural that Used to say that something is natural, expected, or justified. It follows a clause, often with だ or です after 当然.
JA: 毎日練習したので、彼が上達するのは当然だ。
EN: Since he practiced every day, it is only natural that he improved.

彼がジャズに詳しいのは当然だった

It was only natural that he knew a lot about jazz.

我々が興奮したのは当然だった

It was only natural that we were excited.

彼らがハンナにあこがれるのは当然であると思った

I thought it was only natural that they admired Hannah.

彼がそう考えるのは当然です

It’s only natural that he thinks so.

そうおっしゃるのは当然です

Of course you would say that…

— フィールド・オブ・ドリームス (1989)

恐れるのは当然

It's only natural to be afraid.

— ベルリン・天使の詩 (1987)