Was there an intentional plot by the oil companies to mislead the public into believing plastic would be readily recycled, knowing this would be difficult or cost prohibitive and that the plastic would end up in landfills? If so, who is behind this and why?

While this is being attributed solely to corporate greed by Big Oil, it is much more accurately stated that it is a consequence of extraterrestrial mind control manipulation. They are manipulating the energy companies to be complacent about the growing problem of waste plastics and have all along largely kept quiet about the increasing harm to the environment and to living things in particular from such a huge barrage of discarded plastic materials that are harming the biosphere. That complacency is mirrored in government agencies charged with environmental protection as well as the public as a whole, and that is why despite the hue and cry to warn about global warming and environmental degradation, people are still not up in arms other than the most zealous activists. To be sure, the issue of hazards to the environment is embraced by the politicians but that is solely because of convenience to have that talking point at times, to do virtue signaling for purposes of shoring up their base support. That is why many have championed the cause but few have done things of material impact after gaining office. The problem of plastic waste is growing in seriousness but is one of many, many other toxic by‑products of your current technological culture which is orchestrated to be as deadly as possible, but in ways that will largely be ignored through a programmed complacency of the citizenry.