I worked as a software engineer in a big internet company for 7 years in total. For the first 6 years , I had been working at the department of desktop applications. I really loved working there. Really enjoyed the technology and the people at the department.

Unfortunately the department was closed a year ago. During that time, My company bought a small start-up that specialized in mobile applications. Upper management decided that I should be assigned to work in that start-up as a part of the team. I had never worked before with mobile and it was totally new to me.

After two/three months , I realized that I wasn't interested/content with that job. In addition, to being constantly micromanaged by the new boss. Throughout that time , I wanted to find a new job but the current gig depleted most of my energy and my time. Also , due to personal circumstances(mortgage and etc), I hadn't quit and continued to work for a year in total. In the beginning of may, I got fired.

I know that similar questions were already asked here but I think every situation might be different.

Question: How should i answer the question why did i leave my last company after 7 years of work?