It's seems like they've been able to slow down the economic decline, but not stop it entirely. The question is of course, will the fall be greater than it would have been if we hadn't stepped in ?

There's no way of telling, I don't think the policy makers really made a mistake (well, maybe the US ones did, with having their little war during an economic recession). They took a chance, things aren't really turning out as they hoped. Like the author says, economic experiments do happen, and the results can be pretty unpredictable. It doesn't mean they shouldn't happen.