There's a simpler explanation: someone wants to destroy Twitter. (Bless them, lol.)
Twitter's only value to the world is the idea that it is a platform where "celebs" can safely broadcast their message to the public. That value proposition has now been destroyed.
Well, if I was Obama I'd cancel my Twitter account ASAP. Today the tweet is relatively harmless and obviously fake, but who's to say that tomorrow something really toxic to Obama's reputation won't be posted under Obama's name? (Say, something anti-feminist.)
Twitter's only value to the world is the idea that it is a platform where "celebs" can safely broadcast their message to the public. That value proposition has now been destroyed.