-다 보니 — Realization

This expression is used to indicate that the speaker learned something new after doing some action or behavior continuously from some time in the past, or that a certain situation has occurred as a result of that behavior.

The -다 of -다 보니 is the shortened form of -다가, which refers to something occurring in the middle of a continuous action, and 보니 is the shortened form of the combination of the verb 보다 and -(으)니까 which refers to a discovery or result.

Thus, the forms -다가 보니까 and -다 보니까 can also be used to express the same meaning.

Details

When an adjective or 이다 comes before -다 보니 the preceding clause indicates the reason or cause of the event or action in the following clause.

그 일이 워낙 중요하다 보니 혼자 결정할 수 없었어요.

Given the fact that it was by nature an important issue, I couldn't make the decision by myself.

대통령은 한 나라의 대표이다 보니 경호하는 사람들이 많을 수밖에 없어요.

Because a president is the representative of a country, it is unavoidable that he or she will be heavily guarded by a lot of people.

The differences between -고 보니 and -다 보니 are as follows.

Kimchi Reader

Indicates a sudden realization or conclusion while doing an action