Not that you would want anyone to lose their jobs, but it does seem odd that in a short time period you were able to finish an entire backlog.

That sounds a bit like there might have been some overall inefficiencies that lead to needing too big of a team for the work.

When one person even with working overtime and not taking a lot of breaks can complete the entire backlog really makes you wonder if the whole team was efficient and how many people were actually needed.

At least from what I've seen in my career this tends to be a common problem where most teams are inefficient, write buggy code or do other things that they keep hiring more people to handle all the work that is needed. However, if they would have worked on improving and optimizing the current team more work could have been completed with less bugs and less people.