Actually, Google employs 2 of the 3 main authors of the JPEG XL spec, and the main contributors to libjxl.

There people in this thread arguing they have no idea what they are doing and have no expertise, while they simultaneously employ the spec authors to work on it and are one of the two primary contributors to the reference library.

Google is not a monolith. The JXL people are at Google Research Zurich, while the people who decided to not include JXL in Chrome are members of the Chrome team. The Chrome team obviously does not employ the people over in Zurich, nor do they presumably control what they work on.