It sounds pretty unlikely that they didn't get the investment because of the demo going wrong. Investors aren't crazy, they know the product isn't don't yet and

It sounds pretty unlikely that they didn't get the investment because of the demo going wrong. Investors aren't crazy, they know the product isn't don't yet and small things can crash it before it's polished. More likely the management were not convincing about the investment case. Also the thing about being junior, even a bright one, is you go down a lot of dead end paths. You learn a lot, but you also eat up a lot of time. This is the risk of hiring juniors, and the CTO should have known.