This is the 6788th most frequent Korean word.
이유에서였다
"It was for this reason."
This usage demonstrates '이유에서였다' indicating the source or cause of being late.
그가 늦은 이유에서였다.
It was due to the reason why he was late.
Here, '이유에서였다' is used to explain the cause behind their inability to go.
그들은 못 간 이유에서였다.
It was because of the reason they couldn't go.
In this instance, '이유에서였다' conveys the justification for the choice made.