It just as likely, was the abuse of corporate interests by power. That is to say, those in power realized they could shakedown corporations with the threat harmful legislation.
The Myth of the Robber Barons explains that there were corporations who were producing value for consumers without fear, fraud or corruption.
There is nothing inherent in corporations that cause rent seeking behavior. The biggest rent seeking groups are, home owners (mortgage deduction), retired people (Social Security, Medicare) and government employees (Teachers etc.). Not one of these groups has a corporate form. Abolishing the corporations will not remove these groups from the trough. In any case, some corporate rent seeking could be seen as defensive rather than offensive, an attempt to protect themselves from other rent seeking groups. When government is large and intrusive people will always band together to seek favor and protection. Abolishing corporations will not change this.
Having worked for both types, I would say that the "abuses" of employees are far worse under proprietor run/small business than any large corporate concern.
That's untrue. Why else would they engage in it? "In any case, some corporate rent seeking could be seen as defensive rather than offensive, an attempt to protect themselves from other rent seeking groups."
They have a tit-for-tat relationship with one another. One good collectivist turn deserves another...and on and on and on. They have a mutually abusive relationship, which normally leaves We the People directly in the line of fire, and our country paying the price.