The best explanation for why the Bayeux Tapestry might not tell the whole story of William the Conqueror’s rise to power is: It depicts the Battle of Hastings from the Norman point of view, not the Anglo-Saxon point of view.
This response highlights the bias inherent in the tapestry, as it presents events from the perspective of the Normans, which can skew the portrayal of events and actors involved, particularly regarding the Anglo-Saxon perspective.