Propositional knowledge does not make anything happen by itself, but it can help when actually doing something. For example, the venture won't happen by itself, but once it is started, it might be that certain things happen, and you go "hmm, this looks like something I read about". This allows you to make predictions and act upon them, potentially avoiding a pitfall others have already trod in.

To take programming, once you start programming something, you might go "wait, this looks exactly like that theory, and there was a solution", or "wait, here I also need to guard against this problem" --- both things you have not experienced yet. Learning by doing can be quite expensive.