It's true - Standard Oil was just minutes away from closing their doors before the breakup happened.
It depends what kind of corruption we're talking about, nepotism and waste tend to get cleaned out pretty decently in private enterprise, but exploitation along with anti-competitive and unsafe business practices thrive.
Was standard oil corrupt? from my understanding they reduced the cost of oil by a significant fraction. In fact, they out competed their less efficient rivals.
Rep. William Mason, arguing in favor of the Sherman Antitrust Act, said: "trusts have made products cheaper, have reduced prices; but if the price of oil, for instance, were reduced to one cent a barrel, it would not right the wrong done to people of this country by the trusts which have destroyed legitimate competition and driven honest men from legitimate business enterprise."
I think it's very fair to consider them corrupt - they coordinated with other businesses to make competition impossible and, as a result, forced individuals trying to make a living to be forced into bankruptcy through no fault of their own.
Now, business is a cruel world where luck plays a significant role in success, but it's healthy for society for us to try and keep the playing field of business as level as possible and the number of lives ruined by standard oil is a pretty heavy weight.
