Analysis here: https://www.youtube.com/watch?v=_SfXoCj4TLk
TL;DR is that it may or may not be enough to justify it in court if Twitter sues, but it probably is enough to make a court case necessary, and Twitter's board may be reluctant to spend years in court trying to win their case, since inevitably the court case would involve the very public airing of facts like this that would not paint Twitter in a good light.
That's true, and the Twitter shareholders should have realized who they are dealing with. But that does not mean that tying themselves up a court case for several years is smart because it appears that in fact they are willing to sell.
Well, the threat was there to bypass the board of directors, controlled by big long-term investors, and go directly to the shareholders, many of whom would be happy to cash out for short-term gain. So the board was under major pressure to agree, even if they were somewhat reluctant.