A really good piece on the realities of this topic is here: https://youtu.be/badGHJLDpP8
TL;DW: Farmers thought they were voting for cheap labor and a bailout, like they got last time. They also thought that, as wealthy landowners^1^, they were on the "right side" of these disastrous trade policies and were going to be carried through this mess.
^1.^ I struggled with this concept at first. Things have changed a lot since the pre-WWII era that conjures up images of Ma & Pa Kent in a weathered century-home, on a lonely corn farm in Kansas. It's big business now. Good farm land isn't cheap, equipment is expensive, (legitimate) labor is expensive, fertilizer & irrigation costs a lot, pest control costs, crops are risky in general, and so on. When you work out how much money is moving around and what a farm's net worth is, these people are millionaires even if they're not in the black all the time.
Agreed. Considering that the alternative to that is always higher food prices, it's political suicide to not do this.