I think Abraham Lincoln is overrated. I respect his presidency, and what he tried to do but I think his presidency failed in terms of leadership.
Back then the whole legislation process, and representatives from the states were way way different. Naturally the north had a higher population than the south, so the North had more say in the federal government and federal laws.
There was no restrictions on senators or representatives from each state. Pennsylvania obviously had way more people than poor Virginia did so they got more representation which was unfair.
Union legislation was a burden on the Southern way of life for years, this didn't happen over nigh or even in a few yearst it was brewing over a few decades. The North wanted to end slavery in the South while retraining the rights to slavery in states like Maine. It was completely unfair, farming and plantations was the Southern way of life and slavery was essential.
I'm not saying I support slavery but you have to take into consideration that these were different times, different standards and principles, and slavery was key to the Southern economy and way of life. This was the final straw and is why they succeeded from the Union.
Aside from Americans killing each other, in America's bloodiest war where more Americans died than in WW1 and WW2 combine . Not all bad things came out of it, the reunification of the Union and a change to the electoral college were significant. States now had limits on senators and representatives in proportion to population.
Overall Lincoln was a good president, with admirable goals. But I think he's overrated, failed in terms of leadership and pales in comparison to Washington and even Jefferson.