alt Hacker NewsTypescript (2012), lean(2013), Julia(2012), zig(2016), swift(2014)
Languages less than 10 years old are still in their infancy. It's fairly common for the first 10 years of a language to be quite niche.
The Languages bought by large corporations can avoid that 10 years by making it used by decree, that can make it more popular sooner, but it doesn't guarantee long term success,
There is probably a language that exists today that will be a top 50 language in a decade or two that neither of us knows about. Time is one of the best design resources.
Typescript was Microsoft and Swift was Apple, so those follow the same pattern of Go and Rust.
10 years is enough time. The industry was absolutely using Perl (1987) in 1997 and I was using Python (1991) professionally by 2003.
I mentioned Zig already; Julia also feels like it fizzled in a similar way, by getting attention without commensurate adoption.
But I will concede that you're right about Lean. It feels important that it's solving tomorrow's problem (i.e. today's) rather than yesterday's problem.