What would have caused MSFS to be removed?

[TheSevenflyer]

Do you have a steam version?
If so see this:

FS2020 deletes itself and all content - Steam

I can confirm (02/01/2021) that MSFS 2020 will delete itself and all official content if you verify the integrity of local files through Steam. It apparently rubs out all the local files too and they all need to be downloaded again. The only things that remained were items in my community folder (liveries)