I would also add the revenge aspect of Reconstruction legislation. Many Northerners wanted to punish the South before allowing them back into the Union. There was quite a bit of debate/arguing over the ease vs. difficulty states should face in being restored their place in the U.S.
The amendments became a part of the punishment, but also the oaths taken by former soldiers would play a part in that as well, as well as legal action taken against political leaders, allowing former politicians back into office, etc.