Lone Design Club interview questions

I had three interview steps, and they all went quite well. The last was one with the Founder and on that same day, they sent me an offer for the job, I replied to the offer asking a few questions to clarify a few points that were not well explained, and I have never received a response. I tried to call and email them again more than once, but no one got back to me. They ghosted me! I never experienced this high level of unprofessionalism with a company, I am so sorry for them! They are supposed to be known as a start-up that focuses on sustainable brands but they are missing the most essential part of being sustainable humans that respect and value people!!!