Some excellent safety improvements in C++26: hardening the standard library against out-of-bounds bugs, and a safer semantics for uninitialised local variables:
Is there any relationship between language adoption and the size of its standard library?
These days it seems completely orthogonal, but early Java adopters spoke highly of the collections library compared with C++.
Maybe it's the widespread availability of package managers?
I love how the CommonMark Spec has a test suite that's just a JSON array. It's really easy to test a library for compliance, and I've seen developers nerd-sniped into full compliance.
https://spec.commonmark.org/0.31.2/spec.json