An administrator is logged into Data Loader with their own credentials to insert new Business...

When records are inserted through Data Loader without an explicit OwnerId, Salesforce assigns ownership to the authenticated user performing the data load. Therefore, because the administrator logged into Data Loader using their own credentials, the newly created Business Account records will be owned by that administrator.

Salesforce ' s Financial Services Data Loader guidance states that as records are created, OwnerID defaults to the user ID of the user performing the load. If another team member must own the records, the import file must contain that user ' s Salesforce User ID in the OwnerID field.

This behavior preserves the platform requirement that ownership-enabled records have a valid owner while avoiding a failure merely because OwnerId was omitted from an insert file. Salesforce does not prompt interactively for a replacement owner during the Data Loader operation, and an Account record cannot finish creation with a blank owner.

For controlled migrations, explicitly populating OwnerId is still preferable when records must be distributed among relationship managers or other users. However, in the scenario given, no alternate ownership was supplied. Salesforce therefore applies its default record-creation behavior and assigns the accounts to the authenticated administrator.