Casual players realizing what pro players knew all along.
That assassins are generally not viable. They fell of the meta as soon as people realized that assassins are easily countered with proper vision control, right reactions and good support play. Seeing how most assassins can be countered by most supports' kits, they moved away from them and instead went into the way of waveclear mages, that will provide even more AoE damage later on from a distance.
4 years later, casual players realized that a Lulu was always able to polymorph the Zed, Janna was always able to ult that Talon away, and that Alistar can headbutt any threat away.
Guess what people. These things were happening FOR SO LONG now. Why do you have such a big problem with it now?

are all scoring in top 10.