Why is IA so much more Dem than neighboring states?

[Torie]

The main difference between Iowa and Missouri is that the former was largely settled by Yankees from New England who brought with them a more liberal political culture than the Southerners who settled the latter.

Isn't IA mainly settled by Germanic immigrants?

More so along the Mississippi. When my mother was growing up in Davenport, Iowa, in the 1920's and 1930's, the cultural and class differences between the WASPS and Germans was palpable, including considerable neighborhood segregation.