Engine Service Design interview questions

To start with I was told the company didn't have a job description for the role which I found fishy. I then had an initial call with their Business Development Manager where he asked me the regular kind of questions.The company then asked me to put together a detailed and in-depth marketing plan for them. I then presented this over a video call to one of their partners who commented on its great design and also regarding the level of detail and thought I had put into it. Despite this the company then took more than 6 weeks to update me (after a lot of chasing) that they had decided to go with another candidate. It was an incredibly poor experience and made me glad that I had not been offered the role after all!!