The butterfly keyboard was introduced by Apple in 2015 to replace the old scissor design. The butterfly design is supposed to more evenly distribute the pressure on keys and is thinner. The issue lies in the design apparently making the keys prone to get stuck and one speck of dust under the key renders them unusable. This keyboard design has sparked a few controversies including a petition on Change.org to end the design and bring back the scissor design.
Apple Analyst, Ming-Chi Kuo suspects that Apple may be doing away with the Butterfly keyboard and is bringing back the old scissor-type keyboard. A scissor keyboard uses a scissor-type mechanism to make keys quieter and use less effort to press.
In fact, Apple even introduced a thin silicon barrier in 2018 to improve the fact that the butterfly keyboards are prone to breaking from crumbs.
Technically, Apple is not innovating with this step. Butterfly keyboards are indeed thinner and more durable than their scissor counterparts but are irrelevant if they can’t actually perform.