Well this is an unfortunate combination of user error and the lack of proper documentation of Microsoft.
When you let OneDrive backup the folders on your computer, the (desktop, pictures, documents) folders are moved to a new (OneDrive) location on your computer. Before removing OneDrive, you should have put those files back to their old location.
You also must not enable the function "Files On-Demand" because then not all your files are on your computer.
I discovered that when using file history for backup and it didn't backup my files.
Next to a cloud-based backup method it is also wise to have another form of backup (external HDD or something like that).
Well, not an user error if I don't touch the default config, it shouldn't be replaced by any mean... Specially if you don't give any instruction at all.
If Microsoft doesn't say anything, how should I know it is gonna do that? If they show a warning then no issue, but anyways... If 4 GB aren't backed up, why the hell would you delete them?? No way of justifying that.
I have tried other cloud platforms, none replace your user folders. None delete your files if removed. Then, objectively OneDrive is worse than Google Drive for example, just because of the risks u assume while usig it
(Imagine I hadn't use MEGA, I almost had a heart attack lol)
I mean, OneDrive is good if you make a large backup and upload manually, but not for everyday use... (At least for me)