> but how can Goldman's investment banking arm promise anything?

Easy: they lie. Why is this so mind-boggling?

> This is akin to my bank promising some third party that by Friday afternoon I'll have a certain balance in USD or some specific precious metal in my safe deposit box.

You're just explaining why the company shouldn't have believed Goldman. And I agree they shouldn't. But it appears that they did believe them, for whatever reason. Perhaps it was the Goldman aura. Perhaps it was their top .01% sales staff. Perhaps it was knowledge derived from their client relationships concievably allowing them to choose long-term over short-term investors.

Whatever. But Goldman being skillful liars is not some bizarre left-field theroy.