expression
the reason is that ...; because
Used to introduce an explanation or reason, often in response to a question or to clarify a preceding statement. Similar to なぜかというと, but slightly more casual.
See also: なぜかというと
彼は来なかった。なんでかというと、電車が遅れたからだ。
He didn't come. The reason is that the train was delayed.
なんでかというと、それが一番簡単な方法だからです。
Because that's the easiest way.