The answer your looking for is To Preserve Competition Among Business Firms. It prevents a Monopoly which is where 1 company owns all or almost all of the market share. Like PepsiCo and CocaCola They are competition. Without one another the other will rule the market.
What is the purpose of federal antitrust laws? to raise revenue for government programs to preserve competition among business firms to protect domestic firms from foreign competition to provide services to the general public