Minodes interview questions

I applied online, and after 2 weeks I got an Email that they wanna have a phone interview with me. The phone interview went well. I had a talk with their CTO, who introduced himself, talked a bit about the company, and asked general question from me about my background, studies, competencies etc. After 3 days, they asked me to complete a data science task for them. After that, they gave me a feedback that they are impressed with my work and they wanna have a Skype interview, which is more technical. So, after a week, I had the Skype interview with 2 members of their data science team, which went very well and I answered all their questions. Generally, the people with whom I had my interviews seemed really cool and laid back. I had a good feeling during all my interviews and they definitely made me feel like that with their behavior. In the end, they told me that they will get back to me in 5 days, and I should tell them how much I expect for the salary. However, they never got back to me, and when I wrote to them, they said they have other candidates that fit the position better. When I asked them, if they could give me a feedback for my future interviews to improve, they never wrote back. I understand the fact that probably it's difficult for a start up company to go through the visa process for a non EU citizen, but the least that I expected was for them to get back at me timely and tell me that I won't be going to the next step. However, I also understand that they are young and still not in a professional level, to handle their candidates well.