Even if they were an informational service having the DOJ "break them up" would be way more illegal than anything they could directly publish.

You can have a monopoly and not abuse your power, or you can have your monopoly broken up. The Sherman Antitrust act still exists. Law still exists. There are already multiple anti-trust investigations underway by the states, and the DOJ.

There is bipartisan support to break them up. Ask Warren.

What is illegal about enforcing the law?