you’d be wrong, as far as i’m aware. almost all anime in the current system is an adaptation of a manga or LN - the anime comes at the end of the multimedia expansion project.
Or an adaptation of a game; the ones with multiple endings even sometimes receive multiple anime projects to show off aspects of the different paths and different endings.
Adapted from a manga? Sure I guess. And most movies are adapted from books. I'm not sure that qualifies as a multimedia economic model. Is the anime really there to increase sales of the manga? Or is it supposed to be profitable on its own?