The Rings of Power
A massive reason why the show may fail is because of an immediate competitor. HBO made the fateful decision to go head-to-head with another mega-budget fantasy series. House of the Dragon has one-third of the budget for the new Amazon Prime show but HBO has more experience.
HBO decided to release their new series two weeks before The Rings of Power. This makes sense because they want invested fans before their rival kicks off. Nonetheless, if the Amazon behemoth is a hit it will make the lives of HBO’s executives more difficult (via Quartz).