Part of that process however, is that you believe the person who gave you instructions, expressed or implied, has agency to do that. In a corporation, that means they are an officer and have the ability to bind the company into a contract. All that ends the instant you discover the person who gave you instructions no longer has agency to do so (or maybe never had agency to do so). No matter how you look at it, Baker had a responsibility to re-verify his situation and instructions with the new corporate officers once he became aware of the change in ownership. And the entire world was aware of the change of ownership of Twitter.

Obviously this would depend on the exact wording of the contract that Baker signed with the previous officers. But it is not as cut and dried as you imply.