Not only just on the CEO but also in the entire team which do make such idea.It is really important for them to have that knowledge generally rather than basing on their own basic understanding into crypto which having specialty or broad range of knowledge with it then you can somehow assure that they might succeed because most of the time the do really know on what they are doing.
If the entire team has a great knowledge about cryptocurrencies that definitely helps but the CEO is the most important if he doesn't know what he's doing then it is going to be almost impossible to complete the project in the time frame that they set for themselves because he has no idea about the difficulty of creating the project at all, and when you see that most CEOs have no experience in programming then this means that most icos are not going to become successful.