he thinks there is a conspiracy, I don't think there is a conspiracy, but neither of us are absolutely confident about it.

Exactly. I think there is no rational basis for answering your question.

Again, he thinks that because it was possible for them to do it, they probably did it.

Your friend has a distrust of corporate leaders(here I agree with him) and his theory is probably based on his feeling of disgust for their practices. So his theory has probably more of an emotional basis than a rational one. That doesn't mean it is wrong, just there aren't any rational reasons for believing it.