Okay, this person is completely incorrect in their claim about sharecropping. But yes, the US federal government did not think slavery was an issue worth going to war to end. The Confederacy explicitly existed to continue slavery even though it was not threatened whatsoever in the South and more by freesoilers out west, including Lincoln and most “antislavery” activists. The US invaded the Confederacy because the Confederacy picked a fight and decided to shoot first, it was not about any moral ground. The decision to implement antislavery policy as a tactic during the war is more accurately attributed to the growing food and resource crisis the Confederacy suffered relative to the huge advantage that guaranteeing freedom to the overwhelming enslaved population there created.

So, yes, it was good that slavery was abolished as a consequence of this War, but it would be distortive to suggest the Union fought to do that specifically. Solidarity among property-owning classes was a much more influential element in whether war broke out, and was indeed a huge reason why the war did not start until southerners started it despite the many good moral reasons to shut it down.