>Losing even a small proportion of contributors

Wikipedia has been slowly losing editors for ~12 years[0].

[0]: https://commons.wikimedia.org/wiki/File:Active_editors_on_En...

But this was in the hypothetical of Wikipedia being sold or taken over. If people don't agree with the practices of the new owners and rally behind a fork trusted by the community, I expect most moderators and contributors to follow.

PR firms are really good at spinning and diffusing and confusing criticism. Not completely, but enough to split a community trying to rally behind anything that is against their interests.

The sale or takeover would start with promises that nothing would change, and then would change slowly enough that each editor would have a different breaking point and thus be too fragmented to move over at a specific point.