There have been lots of such languages that transpiled to JavaScript or worked on the JVM, adding nicer syntax and features. Many of them went nowhere, but quite a few of them did get widely adopted. Off the top of my head, CoffeeScript was also relatively popular for a while, and Clojure builds on top of both ecosystems, Scala comes to mind too.
Go might be in a similar situation right now, where it has become entrenched in certain domains (like DevOps), and lots of people are not entirely satisfied with it but they can't to switch to something else. Is Go getting a similarly bad reputation as JavaScript or Java to push this through? Is the lock-in as strong as in browsers or Android? No, I wouldn't say it's there yet, but still, it is worth a shot to try to build such an alternative language.
I do agree that Borgo will probably not be adopted widely, the pains it addresses are not strong enough and the language does not seem to be properly maintained and supported. But history shows it is not as unlikely as you suggest.