The major advantage here is that Google merged the development of Chrome OS and Android. It's still Android under the hood making it probably cheaper to develop than having two different operating systems. At the worst case, Google can keep slapping the same Android as the ones on the phones under the hood and just maintain the user interface. They have already promised 10 years of software updates. They can also wait out for it to mature as the Android phone market will keep its development funded. If it will not be successful, any development can still go towards Android Desktop Mode for phones so Google is not losing that much in this direction.