Occasionally you will need more resources or different skilled resources for a project that you have to hand. Sometimes you will need skills in turnaround that your existing team don’t have.
Having a heavier weight interim manager as a “sledgehammer to crack a nut” is a great way of making sure that you are confident that the job is going to be done properly. You also know that you’ve already agreed that you will be downsizing when the project is done meaning that you can keep costs under control.