Linearity GmbH interview questions

It was a 4 month process with several back and forth from the company. They reached me when they open the process, when I was working on the case study, they paused the process. One more after they contacted me again to open the role, they sent a new case study (where I invested several hours and basically outlined the full marketing plan for them). After presenting it, they saying "it was very impressive work" they closed the process and decided not to hire (with all my strategy on their hands). Very unprofessional.