This is just how cloud works -- there are cloud objects, and there are plain files on the cloud file system.

The ways to create cloud objects are with the WL functions like CloudDeploy, CloudExport, CloudPut, or through the cloud web UI, like creating a new notebook or uploading files.

The ways to view cloud objects are with the WL functions like CloudObjects[] or through the cloud file explorer in the cloud web UI.

If you use WL functions to create ordinary files on the cloud file system, they are only visible through WL functions like FileNames.

What makes a cloud object a cloud object is it is registered somewhere with information like its MIME type, the thing that tells the cloud what kind of thing it is so we know what to do when that object is requested (notebooks are handle differently from image files are handled differently from APIFunctions, etc.). While most cloud objects do have a file on the file system, it's that "registered somewhere" that makes them visible to people using the cloud as a web server.

In your case, if you used CloudExport instead of Export, you'd see those exported files in your cloud file browser.

This dichotomy of cloud objects vs plain files is confusing, but I hope this explanation helps a bit. Please let me know if you have further questions.