By the mid-1990s, corporations no longer seemed to have any loyalty toward employees

Very true. I was a lecturer in a Chemical Engineering department at that time. In the late 1980s, the big chemical companies started putting graduates on six or twelve month rolling contracts rather than employing them on a permanent basis. A local senior manager of a major company complained bitterly that recent graduates showed no loyalty to the company and was most put out when a colleague of mine said he wasn't surprised when they, as employers, were showing no loyalty to their employees. Loyalty is a two way thing and if you are not loyal to your employees, why should they be loyal to you?

My daughter experienced the rolling contract business at first hand and eventually got fed up and left her employer, a major chemical company, and went to train as a teacher. She said that about a third of her intake were from industry and many had similar experiences to her.

While the examples I have first hand knowledge of are from the chemical industry, I have no reason to doubt that the oil industry behaved in a similar manner.