This is the primary use. Attackers feed the list into tools like OpenBullet to test the stolen credentials against other websites. It relies on the common habit of people reusing the same password across multiple platforms.
These files are not "official" downloads but are illicitly aggregated data sets used primarily for cyberattacks. Download Combo List EspaГ±a Mix txt
If your information is part of a leaked combo list, you should take immediate action to secure your digital identity. This is the primary use