I wonder if there is some sort of breach of fiduciary duty or securities fraud claim here.

This move seems likely to alienate subscribers (both for potentially being against their ideology, and more importantly, for implying lack of freedom of expression that customers would demand from a newspaper). It is also likely to lose them talent. The move seems to benefit bezos personally by using the newspaper as a mouthpiece, even if the newspaper itself as a business is damaged in the process.