Answer:
because that ment one person controlled the whole industry.
Rockafellers standard oil is an example because he used vertical and horizontal integration to take over the oil business and had no competition
Most people criticize monopolies because they charge too high a price, but what economists object to is that monopolies do not supply enough output to be allocatively efficient. ... The rule of profit maximization in a world of perfect competition was for each firm to produce the quantity of output where P = MC.