Because Iowa picked Santorum last time and Huckabee the time before?!
That's true, but it does not really make the point. Santorum and Huckabee went no where because they were NEVER EVER going to be anything more than just niche evangelical candidates. There is no way either man was ever going to have broad national appeal. Trump or Cruz will win Iowa it appears - and when they do, they will be broad appeal candidates.
In the long run, we don't know if Iowa and NH will be significant THIS go round.....the fact that they weren't in 08 and 12 doesn't mean they may not be this time. I think Iowa is more important, given how liberal NH is.