Well, if the idea of "ad-hominem" is be played out, let's try a new term, "Occam's razor".

Assuming that the claims of support by some businesses for libertarianism are correct, does it follow that "Libertarianism was created by big business lobbyists" in the United States in the 1950's?

It appears that the historical use of the term dates back to the 19th century, so that's quite unlikely.

It's much more plausible that organizations, such as the real-estate lobby found a common objective with the libertarians: reduction in government regulation, particularly rent controls. From the point of view of landlords, big-government Democrats (e.g. FDR) would be an enemy and big-government Republicans (e.g. Hoover) would also be an enemy.  An organization which proposed that government interference was often counterproductive would be seen as an ally.  From the PoV of libertarian evangelists, being paid to promote their own viewpoint would be win-win.

Also, as has been pointed out above, there are limits to the alliance between libertarians and big business.  First, many big businesses (e.g. General Electric, Lockheed, Boeing), while wishing for reduced government regulation in their businesses, are very happy to have a customer who can print up a virtually infinite supply of money to pay his bills. Second, properly formulated regulations can help erect barriers to entry for competitors.  The revolving door between business and government helps to ensure that regulations are "properly formulated" for best effect.  As an example, look at the requirements for setting up a bank or stock exchange.