Self-preservation. I don't mean to overly simplify the equation, but this is capitalism at work. The coach's job security and paycheck depends on winning, which leads to putting ethical behavior as a lower priority -- meanwhile the journalists job security and paycheck depends on keeping the powerful people (coaches) around them happy, so they can keep access to the program to write good stories, which leads to the existence of 'beat' writers who can't afford to risk their own necks. Everyone not well off in the equation has gotta put food on the table, and everyone in positions of power in the equation also have the intoxicating effect of the Ego, which can supersede everything else.
ESPN fired McMurphy - they probably don't want to blatantly advertise that someone they let go is still breaking important news on his own without an employer.