Why is Iowa not a red state?

[DS0816]

Demographically it looks like it should be, it has a similar "make up" to very red states like Nebraska and Kansas. Iowa has never been a very red state though. It was one of Reagan's weakest states in 1980 and 1984. Ford barely won it in 1976. Bush lost it in 1988, Clinton won it twice, Gore won it (barely), Bush barely won it in 2004 and Obama won it twice.

Is there a lot of mining or industry in Iowa compared with Kansas and Nebraska which gives Democrats the edge?

Barack Obama won the white vote in 2008 Iowa. That immediately squashes the connection you've made with Iowa's demographics. The state is more in line with being a bellwether, with about a 2-point Democratic tilt. A Democrat gets elected or re-relected to the presidency of the United States ... Iowa carries.

[DS0816]

Barack Obama won the white vote in Iowa in both 2008 (a Democratic pickup year along with that state) and his re-election in 2012.

Whites are at least 90 percent of the size of the vote in Iowa.

Reason OP should have been able to understand, in the first place, is that whites do not handle their voting everywhere in this country like they do in Texas and numerous Old Confederacy states.