Why were Brittany and Michael told that nobody wanted to continue working with them?
In the survey, other participants indicated that they were the ones with whom they did not want to continue to work.
They were randomly preassigned to the condition of social rejection.
They were chosen for the rejection condition because they belong to an ethnic minority.
They were confederates of the experimenter and acted in a way that guaranteed the other participants would dislike them.

Humans are said to be social beings which means that we survive in part due to our social connections. The experiment from the video was meant to research and evaluate what happens to human beings when they experience social rejection instead of acceptance.

There were four participants being Alexandria, Mike, Brittany and Michael. For the purpose of the research, Brittany and Michael were preassigned to the condition of social rejection whilst the other two were preassigned to acceptance with the goal being to observe the reactions of the parties after they find that they were either accepted or rejected.

Attached is the transcript to the video of the research summary.