Looks like he really is buying it. Why, and why spend so much on it? Because he believes it currently has a lot of value. Could he spin up his own competing product? Perhaps, but would it have the same value that Twitter has today? If you only look at the value of technical utility, then it could be argued that he could create a more valuable platform than Twitter. But Twitter's total value is much more than just its technical utility. It already has brand value, and a number of products & services rely heavily on it. Just think of the kinds of data, human and machine generated, that flow that platform. Why spend money on creating a new platform from the ground up and convince others to interface with it, if you can spend the same (or less) on taking over the existing platform?