Trusts in particular (cooperation agreements between competitors) were entirely a fad of businesses in the 1800s, particularly amongst more progressive-leaning Chairman. It is doubtful they would have had long term success even without government intervention.
https://southerncalifornialawreview.com/wp-content/uploads/2...
We also know that things like predatory pricing and trying to undercut businesses to acquire them was somewhat of a myth. If Standard oil sold for less than you, it was because their operation costs were lower because they were bigger.
http://www-personal.umich.edu/~twod/oil/NEW_SCHOOL_COURSE200...
The enforcement of the Anti-trust act mostly relied on companies suing each other for grievances. But most companies never brought grievances about being acquired.
It was a PR campaign! But for protective tariffs: https://timesmachine.nytimes.com/timesmachine/1890/10/01/103... Sherman himself was pretty open that he wanted to blame rising costs on businesses when a new round of tariffs was passed into law.
