Because he’s an asshole
By 
Facebook employees are not thrilled that Mark Zuckerberg allowed his website to be Radio Rwanda this week:
Frustrated Facebook employees slammed CEO Mark Zuckerberg on Thursday during a companywide meeting, questioning his leadership and decision-making, following a week in which the platform promoted violent conspiracy theories and gave safe harbor to militia groups. The billionaire chief executive was speaking via webcast at the company’s weekly all-hands meeting, attempting to address questions about violence in Kenosha, Wisconsin, and the QAnon conspiracy that has proliferated across Facebook.
The meeting came one day after the Verge reported that a self-proclaimed militia group calling itself “Kenosha Guard” had used its Facebook page to issue a “call to arms” — violating Facebook’s own policies — and remained online even though at least two people reported it before the shooting. It also followed weeks of employee unrest, in which the company’s rank and file have urged the CEO to combat the spread of QAnon-related content on its platform.
One of the many bad consequences of Trump winning another term is that it will probably encourage more media platforms to do what Zuckerberg is doing.