Lincoln wanted all the Confederate States to join back the union and he did that by issuing the Emancipation Proclamation which basically stated that if the Confederate states did not join the Union by January 1, 1863 then all slaves would be freed.
They were seen as Peter’s spiritual heirs.
Nelson Mandela is famous for being a civil rights activist for South Africans. Black lives matter is a movement about rights for all Blacks. Both stand for black rights, though Nelson Mandela was standing up for a specific group of black.