I don’t understand iCloud system

You cannot, iCloud does not work that way.

iCloud is a syncing service not an off device storage solution, that means there's a copy of everything you decide to place on iCloud on the device itself. Deleting the video form the device would then cause it to sync the action and delete the video from iCloud.

Phil’s description is accurate; it’s important enough that it bears repeating.

In this context iCloud is “syncing” service (vice a “backup” service)

Meaning if you inadvertently delete a file … it’s deleted everywhere that syncing is enabled.

This is unlike a classic “backup” in which you could pull the inadvertently-deleted file from yesterday’s “backup.”

Lastly:

You might find this iCloud User Guide helpful:

(click on “Table of Contents”)

https://support.apple.com/en-au/guide/icloud/welcome/icloud

Note that iCloud DOES provide some classic “backup” features.

For example; for your iOS devices:

If you damage or loose your iPhone/iPad …

… the replacement device - upon signing-in - will automatically setup and VERY CLOSELY mirror the device which was lost. (Right down to app settings and screen icon arrangements)