Surprisingly, STEM helped the North win the Civil War [0].
One of the big differences at the time was the use of "repeaters" by the North. Having a gun that can shoot again quickly when the other side cannot is a huge advantage.
With the North winning the Civil War, they put both Reconstruction and the 15th Amendment in place, causing Blacks to have the right to vote (of course many people tried to thwart that law for almost a century).
History is very complicated thing. But the quick spread of the trend would not be possible without communications and expanding transocean travel to name the least.
There are ripple effects with everything, and yes technology always provides disruption, but it would be absurd to say that technology accomplished these things.
