tl;dw: they got lazy at the end of the 70s and started copying their own hits over and over, putting out the same type of shows. Toy companies got involved and

tl;dw: they got lazy at the end of the 70s and started copying their own hits over and over, putting out the same type of shows. Toy companies got involved and created their own toons, with a superior quality, and they were done after that. Cable also hit, and they couldn't keep up with the demand, so also lost additional market share.