A few years ago, Chrome OS and Android were going head to head at Google. Now, it's pretty obvious to see which is the most popular and important to Google. Granted, there's a brand new and cheap Chromebook, but the three Nexus devices are getting a lot more attention.
What's more, Android 4.2, the latest version, is being praised left and right as the best Android ever, unsurprisingly. That said, some people can't be satisfied with what's being given to them so this is how Chrome OS on the Nexus 7 happened.
Famed Chrome OS/Chromium OS hacker Hexxeh, pretty much the only one out there, worked into the wee hours of daylight savings day to give you Chromium OS running (somewhat) smoothly on the Nexus 7, touch input included.
Given that Google has been working on adding touch support in Chrome OS for a very long time, despite the fact that no Chromebook has touch input, and that Chrome OS has a very solid ARM port, courtesy of the new ARM-powered Chromebook, the port wasn't particularly complicated.
Still, it happened and it's working. You can't get to do it for yourself just yet, Hexxeh is working on cleaning up the code and making the whole thing presentable enough for a public release. But it is coming.