It doesn't really matter how inefficient you are if you have the cash to buyout any potential competitors before they have a chance to threaten your bottom line.
In a purely capitalist society wealth (power) accumulates at the top. Money creates money so whomever starts out with the most money tends to win. This is why highly capitalist societies turn into Dubai, with an ultra rich ruling class and a serf/slave class with little in between.
Are you talking about the outlawing of railroad rate rebates or the break up of the company?
Just as an FYI (and apologies if you are already aware of this), but Standard Oil had already lost about ~25% of it's market share by the time it was broken up. Rockefeller had no influence in Texas and California where the wildcatters had moved to and found oil.
In a purely capitalist society wealth (power) accumulates at the top. Money creates money so whomever starts out with the most money tends to win. This is why highly capitalist societies turn into Dubai, with an ultra rich ruling class and a serf/slave class with little in between.