[kbelder]

I don't think they were confident, but they thought they needed to pretend to be confident. Consider it the side effect of presumably competent scientists spending too much time with politicians and PR departments.

And that's why they ended up seeming like liars, and can't be trusted.

[hackerfromthefu]

Well it's not just seeming - they actually were liars, about the degree of confidence. As you said, too much time with politicians and PR professional liars!