His interest was in preserving the Union. Everything else was secondary. Thus, he was in the right place at the right time. But at least he did it.

Probably the smartest man to ever serve as president. I personally think that he had pragmatic reasons for liberating the slaves. I mean, when the Emancipation Proclamation was signed, the war still had another couple of years to go, so it was purely a political act that had no immediate chance of being implemented, the southern states still being under Confederate control. However, Britain (who had been overtly supporting the rebel states for their own reasons) had made slavery illegal the century before so they could not be seen to be supporting a slave state, and withdrew their assistance. It was a brilliant political move by Lincoln, and not necessarily because he really cared about the slaves themselves. I say, though, that there are so many well-intended actions that have evil consequences that we have to recognize those acts of dubious intention that have good consequences. We should focus on the effect, and not the motivation.

There is a school of thought that questions his motives. But whatever his motives may have been one can't deny his impact.