Why was Abraham Lincoln chosen for president?

he was a man who didnt believe in slaveryy./;

First time round - because the Democrats had split into two (North and South), so the newly-formed Republican party was bound to win, with Lincoln as compromise candidate because he was moderate on the slavery question.

Second time round - because there had just been some dramatic Union victories, with Sherman capturing Atlanta, Sheridan seeing off the Confederates in the Shenandoah, and Farragut liberating the port of Mobile.