Maybe the idea is that those who are using those other languages may have other workarounds already?
In either sense, its alot.
(Aside: The backend has plenty of bad languages. For example Python is considered a backend language but is considerably worse than most languages in speed, ergonomics, transitive dependencies, and so on... )
Toolchain weight, integration cost, ease of building DSLs, error message quality ... All those things matter when choosing a language to be embedded as a DSL into another system.
I wasn't really making a comment on that though but rather on overall popularity of TS vs Java, which is mostly just about the influence of the echo chamber and how that distorts peoples perception of what is out there.
Once your product reaches a wider audience you may notice that the balance is different but that doesn't mean that if you had chosen what makes sense for the wider audience (e.g. java) in the first iteration you'd be necessarily at a better place now. Perhaps you wouldn't never get to the place of worry how to please the masses because you product wouldn't have had any success in the first selection environment