Why did Rome have so many bad emperors?

The Roman Empire had many bad emperors for a variety of reasons, including:

Inheritance: Unlike modern democracies, the Roman Empire was an inherited monarchy, meaning that power was passed down through the family. This often led to the appointment of inexperienced or unqualified heirs to the throne.
Political instability: The Roman Empire was plagued by political instability, particularly in the 3rd century AD, when there were frequent changes of leadership and power struggles between rival factions.
Assassinations and coups: Many emperors came to power through assassination or coup, which often resulted in instability and a lack of legitimacy.
Personal flaws: Some emperors were simply bad rulers due to personal flaws such as greed, cruelty, or incompetence.
External pressures: The Roman Empire faced a number of external pressures, including economic crises, military threats, and natural disasters. These challenges often put pressure on emperors to make unpopular decisions or take drastic measures that could harm their reputation.
Overall, the Roman Empire was a complex and challenging political system, and the challenges of maintaining power and stability often resulted in the appointment of less-than-ideal rulers.