In some cases, Office 365/2021 installation may stop because of several reasons like slow internet, server issues etc. Then your machine creates some of files required to office 365/2010/2016 product.

When you try to re-install this time,
You may see issues like these type of office 2019 error code 30088-4 and different series based on the reason of failure.
You have to delete these Office traces from the computer before trying re-installation process.