their determination was due to the fact that they believed in their idea. so it's impossible to had very little to do with the idea
As you say their determination was due to the fact that they believed in their idea - not that their idea was particularly great.
Take Skype, which is one of the companies mentioned in the article. No, they were not the first company ever to do voip. This, of course, begs the question: Why didn't the first movers become huge successes? After all they had a lead of around ten years.
Because of execution.
The reason skype became a success was not that they had an idea that was so awesome the money just started pouring in - it was years of hard work, good design and smartness that got them there. I know that they first tried to raise capital in Denmark, but nobody understood what the heck they were talking about, so they had to move abroad and try there. They were basically so set on the idea that they, after having been put down by almost all VC's in their own country they moved abroad to get funding. Their determination is what made them successful, it had very little to do with the idea.
They might just as well have started a filesharing network and had success with that. Oh wait... They did...