>>957
"the reason being that..." がどういう意味で、文法的にはどういう働きをしていて、
別の英語に書き換えたらどうなるかについては、そのフレーズが出てくる
英文をいくつも読んでいたら、自然とわかるだろう。

(1) What was unique about this flu was that there was a high risk of death for people ages 15-35 years,
★the reason being that★ their immune systems responded too vigorously.
http://maynard.wickedlocal.com/news/20180924/life-outdoorsthe-influenza-epidemic-of-1918-19

(2) You may have noticed that I used the word, “we,” rather than, “I,” when discussing my writing.
★The reason being, that★ although I am the narrator here, most of the articles are about more than just myself.
http://www.observertoday.com/life/sunday-lifestyles/2018/09/column-brings-new-menu-of-options/

そして、だいたい意味が分かったような気がしたら、次のようなサイトの解説を読んでそれを確認する。

(3) the reason being that の意味合いを解説した Quora 上の回答
https://www.quora.com/What-does-for-the-reason-being-mean

(4) the reason being that に似た他のいろんな変形表現を紹介した Stack Exchange 上の解説
https://english.stackexchange.com/questions/342214/the-reason-being