89 years... from 1776 to 1865. Do the maths!
Excuses for why previous presidents didn't support abolition is pointless and irrelevant. The fact is, they didn't and neither did congress... Neither did the courts! States were free to abolish slavery and the CSA didn't have any problem with that. Indeed, the principle of secession was so that states had every right to make this determination on their own.
Ironically, the Constitution of the Confederacy granted voting rights to free blacks and Native Americans... 100 years before the US government passed the Civil Rights Act.
There we go. States rights to expand slavery. See they called them out. States rights to have runaway slaves returned.
And actually the Constitution of the Confederacy did not grant voting rights to free blacks. It didn't recognize them as human citizens. That's why "free blacks" in the south could just be taken and forced back into slavery. That's why not one black person voted in the Confederacy. South Carolina's delegates when it met talked about their outrage that New England states allowed free blacks to vote. They most definitely did not EVER give blacks the right to vote in the South.