Why is Fivetran creating an empty schema named FIVETRAN_%%%%%_STAGING in the destination?
Fivetran creates a temporary schema to do intermediate processing, such as creating staging tables, before the data is uploaded in your warehouse. At the end of processing, this schema will always be empty. This is outlined in our documentation regarding how we Load Data into the Destination.
The schema name will always be of the format
FIVETRAN_GROUPID_STAGING. The group ID is an identifier Fivetran uses to identify each group uniquely.