Let's take your argument to the extremes of ridiculousness - why has pirate got a scammer tag? After all, it was obvious it was going to go bust. So isn't that a "common mistake" between pirate and his investors - as they all knew (or should have known) that it wasn't going to end well?
Because Pirate committed fraud and his customers did not. Otherwise, you would be absolutely right and the blame, and hence the damages, should split between Pirate and his customers.
In this case, both parties had sufficient knowledge to conclude that Patrick had significant Pirate exposure. Total outsiders reached this same conclusion. It was obvious. And there's no evidence of greater fault on either side.
Your other examples are inapplicable. This contract was predicated on a mutual agreement to something that was false due to equal fault on both sides. None of your examples have that characteristic.