All the companies that he had selected to study, were already on the map. They already had an idea, they already had some funding, they already had a viable business model. What killed them was either the execution (team aka internal) or the adoption (timing aka external). But for every such business, there are many others who fail to even get past the seed round or minimum viable product round.
So yes, if you get your idea validated, have a minimum viable product, convince beta users to use it, get seed funding for your idea, manage an accelerator or incubation program to provide you support... then the success or failure of your startup is determined by the timing and execution.
But in general for any startup to succeed you need all five of these factors - Timing, Team, Funding, Business Model and Idea/Vision.