Button Palcements – Why do two types of button placements exist for the same dialog? What is the difference? What are the use cases? [on hold]

So I was asked this question at an interview 2 years ago and I still don't have an answer. The interviewer showed me 2 dialog boxes and asked me to select the one I would prefer to design.

I answered option no. 1. He didn't ask me why i chose the first option. Rather he asked me: Why do two types of button placements exist for the same dialog? What is the difference? What are the use cases?

Any thoughts?