This is one of three positioning statements that you must be prepared to answer skillfully. The employer is trying to determine if you may be an employment problem, whom they don't want to inherit. The question looks backward and it's your job to reassure the screener, then flip it forward, showing the employer how beneficial you can be.
If you were downsized:
"The company restructured, eliminating several positions including mine. This now allows me to bring my skills as an Application Engineer to ensure that your software is up and running
efficiently and customers are satisfied."
If you were fired:
"The company wasn't a good fit for me so with the holidays coming, I thought that I'd spend time with family, and then be prepared to start a new job as a Service Writer, ensuring repairs are completed accurately, upselling services, and enhancing customer satisfaction."
If you left the job:
"I left to explore new industries and new roles. I've determined that being a Project Manager on Solar projects would combine my skills in technology, construction, and leadership and bring greater job satisfaction. I'm eager to show you how I can contribute to your company. Tell me more about the job ..."
Get smooth with your answer now. Practice, practice, practice till it rolls off your tongue!