How does one aspire to become the chairman of a medical department? What career steps are needed to achieve that position

Long road. First you would have to want to care for others by being a physician. So, college, medical school, and residency training. Depending on specialty, that's 11-12 years at least. Then you would practice for several years, gaining experience. If academic, you need to advance to professor. Often involves research, teaching & publications. Also personal characteristics of honesty & responsibility.