>>281322570
When do you think anime was not promotional material for other media? Mecha and magical girl anime have pretty much always been made to sell toys, as far back as the 70s. And adaptations of manga have also always existed. Even if in the past they tended to be more of their own thing (not always) do you think the people involved just ignored that the source material existed? Just like today you would have announcements in the magazine the manga ran in that the anime was airing.

There's also always been multi-media projects, where the anime and manga were made concurrently. It's somewhat difficult to determine for some things if they were decades ago (especially before the internet) if this was the case but I've seen it said for Sailor Moon and Tokimeki Tonight for instance. People think there was some magical time when anime and manga were completely separate and that they were focused on "art" rather than selling something. Even completely anime originals that weren't trying to sell toys were still trying to sell their home releases and other merch.

Pic related is from 1982.