In the grammar explanation for なりに on [japanesetest4you.com](https://japanesetest4you.com/flashcard/learn-jlpt-n1-grammar-%E3%81%AA%E3%82%8A%E3%81%AB%E3%81%AA%E3%82%8A%E3%81%AE-nari-ninari-no/), I ran into the following sentence:

私には私なりの理由があっての事だったんです。

I am curious about one part in particular:

があっての

Is this any different than がある? I know の makes it so that あって describes the following noun instead of the following verb, but why not just use がある instead — which already modifies a noun by default?

The one reason I can think of for using があっての is in conversation when the speaker is not yet sure what they will say next and needs to tie the って to a noun. But I am unsure if this would be the main for using or if this would work with every verb.