As long as the platform follows a proper DMCA takedown, they cannot be sued for infringement. If, however, the platform ignores the DMCA takedown, they lose the

As long as the platform follows a proper DMCA takedown, they cannot be sued for infringement. If, however, the platform ignores the DMCA takedown, they lose the protection they'd otherwise keep under the law and can themselves be held liable for the infringing copyright.