"It wasn't because of A but because of B that ※※ happened."
- "It was because of B not A that ※※ happened"
"it was because of B" 「Bという理由で」
"not A" 「Aという理由じゃなくて」
"that ※※ happened" 「※※となってしまう」
- "It wasn't because of A but because of B that ※※ happened."
"It wasn't because of A but because of B" 「Aという理由より先にBという理由で」