I’ll start by declaring my heavy bias, as someone who dearly loves the Plains but moved east, not only because of politics, but who could never return home in part because of politics.
Many Midwesterners are religious and most oppose pregnancy termination. Some think it should be legal but still discouraged socially, but the default position is “it’s immoral” and the default position within that is “and should be illegal”. To this mindset, which I used to share, it really is murder. Not “equivalent to”, but the thing itself.
Now it used to be that South Dakotants voted mostly on local issues locally and for whoever kept the agricultural subsidies rolling in federally. We had D governors and Tom Daschle was the Senate Democratic leader.
But as the religious right got further and further in bed with the GOP at the national level, the RNC got better at manipulating religious voters. And it wasn’t hard to notice that a lot of us would forego a bit of self interest for the greater good, like outlawing literal murder (to our minds). And so the national money started rolling in, hammering the issue of reproductive healthcare further and further into every race, especially those with powerful D incumbents like Daschle. I had moved away for college by that point but by the time I graduated SD was blood, and I mean blood, red.
(Caveat: unlike most states, these days SD is solid red in urban areas and bluish out in the lower-population rural areas. Can you guess why?)
From there, the ground was fertile for the Tea Party to sow the seeds of populism that our recent President so ably reaped.