It also didn't hurt Rockefeller in the slightest. To the contrary, he actually became far wealthier post-breakup, possibly because all former business units became more efficient in the light of open competition.
Many of them live on today, such as Texaco, Chevron, and Mobil.
https://historyincharts.com/the-legacy-of-the-breakup-of-sta...
https://www.britannica.com/topic/Standard-Oil
In general, trustbusting almost never actually works as planned, but it always seems like a good idea -- a desperate solution, perhaps the only possible solution -- at the time.
The only thing that tends to work is upstart competition driven by new technology that blindsides the older company.
When it comes to a monopolist, the one thing that we can say historically is that, "This too shall pass."