I guess I wouldn't think of cmake as a bubble, it's a part of the ocean the bubbles float in. Blaze/Bazel are a bubble, the only place they see a lot of use are Google-involved projects.

Facebook, MS, Bloomberg, are heavy into CMake. Bloomberg notably so, and MS built vcpkg which is basically a CMake package distribution system. Netflix is mostly a Java/Scala house, and what C/C++ they do have sort of uses a "whatever" approach to build systems (variously, make, cmake, bazel, bash scripts, *gradle*).

"Where is CMake used" is a difficult question. Everywhere.