Funny thing about that de-regulation that led to that huge surge of childrens tv shows designed to sell kids stuff. That effect of it was really very transitory. It would make a good Big Picture episode to actually look at the various standards for tv programing for kids over the years. Starting with why kids cartoons were pretty much limited to Saturday morning before noon. and how it all evolved as a result of regulatory meddling.
But here's the weird thing about that de-regulation, and that wild west of animated toy pimps that it spawned. It was very very short lived. Look a little wider. There was some craziness for a few years in the 80's. Say 82 to 87-88. But then it all went away. It was self correcting market. As you saw with the Transformers movie, people and in particular kids didn't buy it. Don't forget shortly after that surge of kids shows selling little blogs of plastic, we suddenly started to see a new wave of what can best be described as quality shows. Stuff like Disneys afternoon wave of Ducktales and Tailspin and Darkwing Duck and Chip and Dales Rescue Rangers and Gummi Bears, etc etc. Shows like Fraggle Rock. And then the surge of things like Nickolodean, Disney Channel and Cartoon Network. That same de-regulation that brought those massive toy commercials into existence just as quickly killed them off as the networks figured rather than wasting whole hours selling somebody else's product, they could actually sell their own, and get other people to pay them for commercials while doing it. Instead of the product being a He Man plastic toy. The product was now teh media company itself. Disney, Nik, etc. It's a model Sesame Street had been using since the 60's. And it is the same business model that Disney or any media company has long operated safely and successfully under.
I don't think those types of shows died out in the 80s like you suggested. I still remember Mighty Max (as crappy as it was) and Beast Wars: Transformers.
By the beginning of the 90's they were pretty much gone. Yeah some of the key successful properties still had shows. But even Beast War's Transformers is a great example of the shift. The show was less about directly selling toys (virtually none of the show designs worked well as toys, and by the second series they had all but abandoned the toy lines), and more about the property itself. The studio that made it wasn't really a toy driven studio. They made reBoot and Starship Troopers. With the exception of certain Japanese imports (Pokemon), most US produced shows were no longer being produced specifically by or for the toy companies. (Power Rangers weirdly went the other way. It was a cheap Japanese import show that ended up driving toy sales and toy imports. It wasn't made to sell toys specifically. At least not originally. That was an unintended happy outcome).
Most of the companies that had been producing the toy shows and the toy companies that had been funding them were in deep trouble. Filmation went under. Mattel was almost driven under (in part because of the escalating costs of the HeMan movie, another worthy Big Picture subject). Rankin Bass (Thundercats, Silverhawks, Tigersharks, in addition to the classic Rudolf, Frosty and Bilbo Baggins) went under, and their properties were absorbed by Warner Brothers. DIC found far better success making non toy shows such as Inspector Gadget and Captain Planet. Once again pushing their own brands rather than the toy companies. By the 90's Disney had absorbed them.
And key in all of this. Disney, Warner Brothers, Nikolodean etc all had far stronger interests in their own brands and own brand cohesion then they did in pimping plastic toys, at least in the non subtle way of the 80's shows. (Disney in particular is the true master at selling stuff to kids. Just look at anything with the word Princesses. They just do it with a greater degree of subtlety.)