the message scoping issue was that instead of implementing a separate endpoint for scoped messages, Eugen tacked it on an endpoint for public messages, which meant the failure state of GS instances not understanding scoping was to make private messages public. This made all existing GS instances the "bad guy" for ignoring scoping.
Another decision that made GS the bad guy was the initial resistance to separating out local from federated timelines, which led to a shitload of mastodon people thinking they were being invaded by GS people. We literally could not get out of Mastodon people's faces if we wanted to, because of Mastodon's design. Not seeing the boundaries between servers didn't change the fact that some people were just assholes, but at least separating them reduced perceived turf wars. The NIMBY effect was in part because of this too.
The last thing I'll mention is that the "new" GS servers when they showed up got into conflict with most of the existing GS servers. Those servers banned people, silenced and sandboxed users on remote instances. Once those boundaries were set, relations between the servers cooled down into a live and let live attitude. Many Mastodon servers have been far more aggressive, engaging in organized slander campaigns against servers and individuals.
This note is in response to Trev's note, which I mostly agree with and consider my perception of events above supplementary to.