Because Rubio is a boy of average intelligence with a cheerleader wife. Cruz has an IQ of 150 and organizational skills as good as Nixon. Trump is Trump and has proved he’s not afraid to call a bitch a bitch. They want Rubio!
Saying that Iowans are more religious or NH more secular is now a matter of a few percentage points.
If Rubio can sell his schtick in Florida, then he can sell it in NH, Iowa, Utah, California, Wyoming, etc.
Yes there are differences between the states, but I think that well-run campaigns and MSM lies can even out the differences.
Also, a lot more people are willing to vote strategically rather than with their conscience. I have a feeling that the vast majority of Republicans that voted for Rubio in Iowa did so not because they agreed with his policies the most, but because they thought he has the best chance against Hillary in November.