Because Republicans put more money back in the pockets of low wage workers with kids. Most people don't have the luxury of voting along idealistic lines, they vote based on finances out of necessity.
Low-wage workers with children were those most hurt by the Obama's ACA Mandate penalty tax, piled on top of not being able to afford health insurance. Republicans removed that ACA penalty plus doubled the child tax credit. People who afford health insurance are out of touch with this segment of people.