Yep. Instead of putting forth any effort at all to prevent what they knew was coming, they did nothing and let it happen. It's almost as if they wanted it to happen because they saw it as an opportunity rather than a problem to be dealt with.
I do think that this one may very well the the straw on the open borders. The American people want the borders closed, but no one else in Washington does. Every time the talk of securing the borders come up, the talking points shift to two things: The border is safer than it's ever been in history (kind of like this is the most transparent presidency in history, just keep repeating it and people will eventually believe it), and immigration reform that deals with immigrants already here, a path to citizenship, amnesty, whatever. People are tired of hearing and those inside the Beltway may be forced to do something, if only in the short term until it leaves the American memory.