Four years ago, David Zaslav clinched a debt-heavy deal to merge cable mainstay Discovery Inc. — which he’d run since 2006 — with what was then called WarnerMedia. The story he told investors was that the two entities’ diverse array of media assets “are better and more valuable together.” He doesn’t believe that anymore.

Warner Bros. Discovery said it will separate its media businesses into two new companies, with cable in one and streaming and studios in the second.