I'll answer with a quote that's commonly misattributed to Goethe, but it's powerful and accurate regardless of who said it:
Until one is committed, there is hesitancy, the chance to draw back. Concerning all acts of initiative (and creation), there is one elementary truth, the ignorance of which kills countless ideas and splendid plans: that the moment one definitely commits oneself, then Providence moves too. All sorts of things occur to help one that would never otherwise have occurred. A whole stream of events issues from the decision, raising in one's favor all manner of unforeseen incidents and meetings and material assistance, which no man could have dreamed would have come his way. Whatever you can do, or dream you can do, begin it. Boldness has genius, power, and magic in it. Begin it now.Perhaps "passion" is synonymous with "commitment" here and elsewhere. Because for developers and others in startups, the challenges are so many and so daunting that only commitment will carry one through. That's why many/most people in this industry (or others) don't do startups - they might be perfectly capable skills-wise, but it takes more than skill to play the startup game.
Money and even new ideas can be acquired later. Passion you have to start with and finish with. You may find yourself seeking more money (look at all the B, C, D rounds, I have even seen a G round). Ideas morph and are even thrown away in favor of others. But passion is the ever-present characteristic of those who succeed.
Since going through a personal startup business failure, I have acquired the opinion that management skill at every level is the most important attribute for a startup team. It is possible to make a lot of money from a very simple product if the participants understand how to run that kind of company. Conversely, without management experience on the team, the chances for success are very low. Note that the person or persons with the management experience do not necessarily have to be part of the original group of inventors or concept-creators.