Why were so few violations of the sherman antitrust act brought to court?

The US antitrust law was passed by congress and aimed at regulating the competition among enterprises. It was named after the senator John Sherman of Ohio. He was chairman of the Senate finance committee. Other states also passed similar laws but they dealt only with interstate business. It was meant to end the monopoly of Trusts in major industries which was affecting the competition. This act failed and very few companies were brought to court. The major loophole of this Act was that it didn't define the terms "Trusts", "Combination", "Conspiracy" and "Monopoly". The companies who were brought to court got free easily. One such case was the case against the American Sugar Refining Company, which controlled 98 percent of the sugar refining. But the court still ruled in the favor of American Sugar Refining Company.