I think it can be "uniquely credited" because another book or song lyric didn't get you to that insight. We live in time linearly, by necessity we have to experience something before or after something else. At that point it just seems like common courtesy to at least partly credit the author for some of that experience. People definitely can get carried away, turning the author into some holy person because of the experience you had reading their book isn't good. But when I look back at books or any work of art that I learned something from, I still appreciate that work (and by extension the creator) because of the path it put me on.

Sure it's all fundamentally chance, but it's like when you're hungry and you eat a pizza, that pizza did fill you up even though a hamburger would have done the same thing. It's not weird to credit the pizza in that situation.