Almost the entire early large scale adoption came from people writing async web services.
From 2023:
> In that regard, async/await has been phenomenally successful. Many of the most prominent sponsors of the Rust Foundation, especially those who pay developers, depend on async/await to write high performance network services in Rust as one of their primary use cases that justify their funding.
Keep in mind that one requirement is being able to create things like Embassy.
https://github.com/embassy-rs/embassy