They didn't do a 180. They were never serious about enforcement.
Take a look at those rates of illegal immigration. They only seriously went down when the border fence was partially completed between San Diego and Arizona. That's why you see that big drop ending in 2010.
The fact is that Democrats love as much immigration that they can get, legal or otherwise, and this is why:
Legal immigrants can vote immediately upon getting citizenship, but illegal immigrants can birth children who can vote. This is the scam. It's all about politics. Once you realize what's going on, you'll never look at this issue the same way.