Ummm, no.
Your logic is extremely faulty.
The Iowa straw poll doesn’t determine who wins.
It only determines who gets to continue on, and who has to drop out.
And it does not treat all candidates equally.
The Iowa straw poll tests each candidate uniquely, based on where they are in the race.
For Pat Robertson, winning the straw poll didn’t mean he was on track to win the nomination. All it meant was he was able to survive another day. Just like not winning didn’t hurt GHW Bush, or Reagan before him. Their overall strengths carried them, and unlike the second tier candidates, they never depended on Iowa as a springboard for their campaigns. Their campaigns were already flying high.
Iowa isn’t about picking the winners. It is only about sifting out the losers.
If Iowa doesn’t predict winners successfully, why should anyone pay attention to it in predicting losers? Reagan lost in Iowa but won the nomination. Etc. It seems to me that candidates with strong religious communities supporting them do best in the poll because they have the most motivated grass roots for this sort of contest. That doesn’t tell you much, but it explains Robertson, Romney, and Huckabee.