File is missing from icloud

iCloud is a data storage. so why are files disappearing from it?

If you have installed that the documents folder is synchronized with iCloud, then the files that you have on your mac are synchronized with iCloud and correspondingly they are also on iCloud (since this is a remote data storage provided by apple)

and you can view all these files on all your devices.

and the problem is not in backups at all. The problem is that files are disappearing from iCloud

You are talking about simple things that are done first.

This file is not in the trash, nor in icloud, nor on the Mac. I did not delete this file and only I have access to these devices.

I fully trusted iСloud to store important files

I don't create backups. since I keep all important files on iСloud