Morph targets are not exactly used for optimization… a typical morph target is basically a snapshot of vertex positions so you can use for more complex deformation on skeletal meshes where you would otherwise need hundreds of bones.
I think you’re referring to vertex animation (which is basically the same and sometimes called static mesh morph targets), you can bake animation frames (vertex positions) to a texture and then make a static mesh animate via material world position offset (static meshes can be a lot more performant than skeletal meshes, therefore you can use that technique for optimization).
Note though that animating static meshes from a texture has a lot of limitations… it’s not like you can replace skeletal meshes entirely with this technique.
Here are relevant links.
