No, but you can fault a party for making an impossible claim.
Absolutely. And I do fault Patrick for making impossible claims.
If I lie to you, are you equally at fault if you believe it? Maybe you do believe that, but I don't. I think the liar bears the moral responsibility for lying. Maybe Harnett didn't deliberately set out to deceive anyone, but he made various untrue statements. He made the statements. He bears the responsibility for making them.
There's no evidence Patrick lied about anything having to do with this arrangement. And I agree, he bears the responsibility for the false statements he made.
In this case, there was a shared mistaken belief on which the agreement was based, without which neither party would have entered into the agreement.
You speak as if this shared mistaken belief came out of nowhere. It came out of Harnett's mouth. Yes, it was a shared belief, but if Harnett didn't make the proposal then the deal wouldn't have been made. Harnett made various assurances. He assured the impossible. We can't blame him for not making good on his impossible claim, but we can fault him for making it in the first place surely?
Yes, and I do. However, I place roughly equal blame on those who believed that what Patrick was claiming was possible. It is substantially the same mistake. There's no significant information that Patrick had that those who invested with him didn't have that had any relevance to the question of whether his basic business model was sensible.
Those who invested with Patrick made precisely the same fundamental mistake Patrick made, in precisely the same way, causing precisely the same harm. I want to hold them responsible too. You seem to think I'm trying to excuse some fault on Patrick's part. Absolutely not -- I do not excuse anyone who believed that Patrick's business model was sound and risked people's money on that basis.