Abraham Lincoln was actually one of the more moderate Republicans in the party. He was not an abolitionist—unlike Salmon Chase, one of his rivals for the presidential nomination. Lincoln definitely did not endorse civil rights for African Americans, either, as he intended to create a colony of former slaves in the Western Hemisphere. Lincoln's only goal was to limit the spread of slavery into the Western territories. Southerners feared that this would lead to slaveholder's interests losing the balance of power in the Senate, and this ultimately led to secession and war.
Lincoln did speak out against slavery, most notably in his "house divided" speech, where he claimed the nation could not exist with half the nation supporting slavery and the other half condemning the practice. Lincoln himself did nothing to cause the Civil War; he was elected by less than half of the popular vote, and most Southerners did not like the Republican party in general. Lincoln did pledge to uphold the Constitution and the Union, and this meant that he would not stand idly by and let the Confederacy leave. This was ultimately what led to war—it was Lincoln's willingness to stand up for preserving the Union.