Compared to Rust where my experience with protobuf lib some time ago was that there is a choice of not 1 but even 3 different libraries, one of which doesn't support services, another didn't support the syntax we had to support, and the third one was unmaintained. So out of 3 choices no single one worked.
Compared that to Maven, where you have only one official supported choice that works well and well maintained.
It's even more pronounced with the main Java competitor: .Net. They look at what approach won in Java ecosystem and go all in. For example there were multiple ORM tools competing, where Microsoft adopted the most popular one. So it's even easier choice there, well supported and maintained.
That's still consolidation, and it also needs time.
Even in Rust crates like hashbrown or parkinglot have been basically subsumed in the standard library.
Besides consolidation point, I still think that "barrier to entry" point is still valid -- if it's more effort to even publish a library, its author is probably more committed already.
Kids today don't know how to do that anymore...