Regardless, unless discovery finds a smoking gun that the board acted in bad faith vis a vis the charter, which nothing public indicates, a judge would likely tell investors to pound sand.
Note this key quote by Nadella:
"“As a partner, I think it does deserve you to be consulted on the big decisions.”"
That's one way to look at what might be grounds for a suit. He could be wrong, but that won't stop them from suing to establish that fact and they have very little to lose.