Linux Foundation is made up of corporations. This should not be a surprising outcome when you think about it that way.

Edit: https://www.linuxfoundation.org/about/members

And the Chromium supporter group is just a subset of those corporations.

Several leading organizations have already pledged their support for the ["Supporters of Chromium-Based Browsers"] initiative, including Google, Meta, Microsoft, and Opera.

Reminds me of the Open Source Initiative. People tell me that licenses like the SSPL aren't open source because the OSI says they aren't. I tell them to look at who comprises the OSI. Nobody has yet showed me a reason why we should believe the OSI when it tells us what open source is or isn't.