IMO, as a C++ developer, Swift makes the most sense to me if I were looking for a safer alternative.

I think people prefer what's familiar to them, and Swift definitely looks closer to existing C++ to me, and I believe has multiple people from the C++ WG working on it now as well, supposedly after getting fed up with the lack of language progress on C++.

The most recent versions gained a lot in the way of cross-platform availability, but the lack of a native UI framework and its association with Apple seem to put off a lot of people from even trying it.

I wish it was a lot more popular outside of the Apple ecosystem.