That is because LoL character's hitbox are a circle on the ground UNDER the character due to the fact this game is calculated entirely in 2-D and everything functions as if it's circles crawling on a board, while the animation display attacking the player on the upperbody, such as how Thresh's hook appears ON TOP OF his victim after the hook successfully lands UNDER him (by touching the circle under the feet of the character).
This is the most evident in the 3rd picture of the lineup in the OP.
This drastic difference between calculation and animation creates a giant visual angular mismatch, and is incredibly misleading indeed. This issue becomes especially worse when elevation of the terrains (that actually don't take elevation into calculation) is also involved.
Riot should either finally add in a 3rd axis, or redo the animation to reflect a better matching between calculation and visuals so this kind of issue is nowhere as extreme as this particular case.