It is never possible to have all animations in the downloaded zip.
I have downloaded a lot of models and all of those models contained only 1 animation.
For example, https://sketchfab.com/models/d24d19021c724c3a9134eebcb76b0e0f
I downloaded it, imported into unreal engine, and there is only static pose, no animations.
Another examples are posed models that also offer t-pose pose. There is never tpose in them, there is only 1 file with posed animation. Why does sketchfab eats the animations?