OK, I admit that IDK everything about the geopolitics of this. I've read some books but it's been years...but we were already involved in supporting South Vietnam and then after the monks were self-immolating, we supported a coup of Dinh Diem. This is a guy we had previously supported in preventing free elections, and then we flipped on him.
You are right that correlation is not causation, but we got a hell of a correlation here, and I'm confused about why you are concluding that it had no impact. Based on what?