1. Lincoln genuinely believed that the war had been about slavery and thought that compensation would promote healing so felt he had to try.
2. Lincoln thought compensation was due Southerners and thought he had to try because he believed it the right thing to do.
3. Lincoln felt the overture was a good gesture of reconciliation even though would not succeed.
4. Lincoln knew there was no way it would succeed so he cynically pushed the proposal to build his credentials as a generous conqueror.
5. Lincoln was losing it.
Any other possibilities I'm missing here?