As an ex-Amazon, I just failed an amazon contractor interview

I am an ex-Amazon and I am in Canada. I just failed my first round contractor interview last Friday. I left Amazon because I doubled my TC but unfortunately I got laid off 3 months ago. I got this interview because the contractor role requires candidate to be ex-Amazon. The first round is with hiring manager of staffing company. The HM failed me at the end of the interview and told me that "there are better candidates", and "I failed to answer to the point". I am not upset by the feedback. The only frustration is that I think I don't fully understand what is the rule/standard/expectation of HM. When I interview for full time position, I know there will be behavioural questions / coding / system design and they are looking for specific signals. However, with this kind of contractor interview, my feelings are, either the HM want to fail me or I don't understand what signals they are looking for. I was also asked design patterns like chain of responsibilities and open-close principle. Am I expected to know all design patterns in detail and be ready to talk about each one? I know many and I know open-closed "open for extension closed for modification", but if you ask me elaborate I do need to check some articles. Can you share your experiences in contractor jobs/interviews? What do you think in general HM in contractor roles are looking for? I right now have a feeling that FTE interviews are easier for me. At least, I know what it should look like. Unfortunately not many US companies are hiring in Canada so I either interview Amazon jobs or local Canada companies. I am also feeling sorry for myself and other ex-Amazon people that we are fighting for Amazon contractor roles. #amazon #contractor