Clearwell Systems interview questions

First had a phone interview with an engineer in Colorado. Asked how I would implement a concurrent hash map, Java coding, JVM GC etc. Then interview with Architect was silly. Three more engineers, then VP of Engineering and Founder CTO. Loved the company vision, passion and energy of the CTO. Felt very happy about hearing the higher purpose of the company directly from the founder. The whole process was very unpredictable - didn't have a clue, but a recruiter called me to let me know I made it. Was happy, but the salary/comp negotiation was a big turn-off.

I went through the technical phone interview where they asked mostly Java knowledge questions, and then a small coding question. Then I was invited onsite where I was interviewed by 4 senior engineers. They asked about my experience, and also algorithm questions - linked list, designing a system, concurrency, immutability, priority queues, etc. All of them seemed to like my answers, and so I was invited for the next stage - meeting with the Senior Director, Development and VP of Technology. The Senior Director of Development was not very nice. He was doubting and rejecting my every answer, which I considered to be rude. I was "left with a bitter taste in my mouth" after that interview. A week later I received a rejection email. I just don't understand why they don't trust their senior developers who interviewed and liked me, and why 1 person decides whether to hire or not.