>>9992086>>9992264>>9992281The genesis of this is actually really interesting. Basically Kenner wanted to have more figures than what Toy Biz was stuck with in 89(which just had three). They weren't allowed to depict Batman in colors they hadn't before. But one Kenner employee used this and the rainbow Batman comic to justify Batman having multiple color costumes before, and it sold well for the Dark Knight collection and the Batman Returns line, so they used it as a model for later series as well.
Keep in mind before TDKC it was fairly rare for a single comic character to get a full toyline. A lot of superhero toylines were collections of heroes(Mego in general, Secret Wars, superpowers). Even the Warlord comic based toyline from Remco used heroes outside of the series.) And since Batman's gimmick is relying on gadgets, be makes for a much easier superhero character to make gadget based variants off of as well.
The Batman cartoon attempted to do more of these toy variants in animation(mostly as single episode gadgets) but that gradually got phased out.
