I am not speaking to this specific case - the court will do that in time - but there is an inherent social problem that business entities need to consider carefully.
On offline example is a stylist or realtor that leaves one shop for another - often many of 'their' customers follow them if the switch is local.
Online examples are commentators/editors that leave one imprint for another - again many of 'their' readers follow them.
What a company needs consider extremely carefully is how to structure their communication outreach to minimise such loss. And contracts alone may not suffice.
Regardless it is entertaining to read about the incompetence/ignorance of those who are supposed to know their stuff:
...eight months later the company filed a lawsuit...
Guess it took awhile for them to notice an impact from Twitter cessation...