Question: Is it so that many Buddhas were once Kings, before they renounce their status? Is monarchy the most common form of government in many worlds? Are there democracies?
Answer: Many Buddhas-to-be were once kingly or princely, to reflect their great good karmas accumulated from their past lives. Their renunciation represents realisation that worldly wealth and power is inadequate for True Happiness.
The title of ‘King’ can be thought of as a placeholder, referring to ‘leader of a country’ in general. This is not so much about the form of governments. Would it not be more ‘strange’ if relatively modern terms like ‘Presidents’ are used in the sutras?
Even if there are monarchies, not all Kings are bad, or with poor kingdoms. Even in democracies in this world so far, there is no perfect elected President. Despite running what could be monarchies, Wheel-Turning Noble Kings (转轮圣王) are the best Kings as they rule with the Dharma.
On democracy in the Buddhist teachings, on how even a kingly figure can be chosen, see part 1 and 2 of https://thedailyenlightenment.com/2010/03/how-were-the-%e2%80%98first%e2%80%99-humans-%e2%80%98created%e2%80%99-part-1-sutta-summary.
