Short answer is yes. Here's the longer answer:
Those non-slaveowning Southerners with sufficient economic acumen knew that slavery was the foundation of their economy. If slavery were abolished, their economy would crumble and everyone would feel the pain. What chunk of the 75% understood this, I cannot say.
But here's a more important reason. FEAR. All Southerners, slaveowners or not, lived in fear of what might happen if 4 million slaves were freed - possibly with vengeance in their hearts. What would become of their womenfolk? This fear was stoked by Church pastors who convinced them that slavery was the Biblically-correct order of things.
As the linked historical analysis puts it: "
The institution (of slavery)
was not just a necessary evil: it was a positive good, a practical and moral necessity. Controlling the slave population was a matter of concern for all Whites, whether they owned slaves or not."
Another key motivator of non-slaveholding whites was status. From an 1860 pamphlet:
“In the Southern slaveholding States, where menial and degrading offices are turned over to be performed exclusively by the Negro slave, the status and color of the black race becomes the badge of inferiority, and the poorest non-slaveholder may rejoice with the richest of his brethren of the white race, in the distinction of his color. He may be poor, it is true; but there is no point upon which he is so justly proud and sensitive as his privilege of caste..."
So yes, the South fought to preserve its homeland and way of life - which was inextricably intertwined with slavery.
https://www.battlefields.org/learn/articles/why-non-slaveholding-southerners-fought#:~:text=The collapse of white supremacy,survival of the white race.