Complex sentence: Mayer became a founder and chair of the National Film Preservation Foundation in 1996, where he was responsible for preserving more than 2,000 orphan films, films whose original copyright had expired or otherwise lack commercial potential sufficient to pay for their preservation.
Split into simpler sentences: Mayer became a founder and chair of the National Film Preservation Foundation in 1996. In that capacity, he was credited with enabling the preservation of more than 2,000 orphan films, films whose original copyright had expired or otherwise lacked commercial potential sufficient to pay for their preservation.