Impact
The impact provided by Ethers has been a simple and popular developer library.
Many aspects of Ethers favour simplicity and safety-by-default, such as "garbage-in, fail loud" (opposed to "garbage-in, garbage-out", which often results in unsafe or error prone behaviour) which has helped protect developers and end-users from innocent mistakes, which could be costly or dangerous in the the blockchain world. Making it difficult to build a foot-gun is a feature.
By being so widely used, it has also led to the development of many other projects on top of it, further expanding the ecosystem.