I'm sure Thread Group would love to stop Google making OpenThread available, but unless they want to tee-off against Google's legal team over patent infringement, the easier route for them is just threatening everyone else out of using it.
All the combined wealth of every individual who has ever wanted to tinker with Thread is a fraction of Google's warchest.
> I'm sure Thread Group would love to stop Google making OpenThread available
Google is a founding member of the Thread Group. OpenThread exists publicly because it's the only widely available implementation that's shipped in a lot of places. Nordic's SDK, for example, uses OpenThread.
OpenThread is built by and for members of the Thread Group, and used by them. It's fairly clear that Google doesn't care much about anyone else.
All the combined wealth of every individual who has ever wanted to tinker with Thread is a fraction of Google's warchest.