Hello,
Business rules trigger for each object separately, even if a bulk operation is performed on multiple objects. In your case, the business rule triggers, and the script is executed for each user whose password is reset. If you need to export the property values of all users whose passwords were reset, you can get the values of a single user and append them to the export file in the script. To do so, specify the -Append parameter in the Export-Csv cmdlet.