Why does Nietzsche reject the idea of a common good?

Nietzsche believed that the concept of a common good is used by those in power to suppress individuality and elevate mediocrity. He argued that the pursuit of a common good often results in the suppression of the unique and creative expressions of individuals, which is detrimental to human flourishing. Instead, Nietzsche emphasized the importance of self-overcoming and the pursuit of personal Excellence.