His problem was that he didn't even bother with Iowa because he knew he would lose. It made the campaign appear to not care about the entirety of America, or perhaps it just exposed the cold calculating that takes place in every campaign and made it too palpable for the voters. In other words, he threw it in voters' faces. I doubt anyone will ever try that again. You can say, "We just want to place well in Iowa and move on to New Hampshire," but you can't say "We're not going to waste time in Iowa and New Hampshire but instead focus on states with more votes".