It's possible that some of these games had paying user retention numbers such that maintaining customer loyalty among the holdouts was not a hard requirement. I don't have a convenient way to look up MAUs at the moment, but many apps languish at say 10k. That would imply a few hundred paying customers. The majority of them would be worth whole tens of dollars in LTV.
One of my rare compliments to Zynga: they aren't stupid and it is highly, highly unlikely that the live teams' business analysts made a worse decision based on the data than an outsider would make based on a press release.
I think it would be a straight numbers decision as you guess. A lot of companies would worry about how this would impact those high value and long term customers and how it could effect retention in other games and future projects. I think Zynga is passed that point now though (if that ever was a concern for them, they have never really been a games company a rational person would have a strong connection to).
Pretty much all the big name MMOs released in the past 10 years have gracefully downsized and maintained maintenance for the player base.
One of my rare compliments to Zynga: they aren't stupid and it is highly, highly unlikely that the live teams' business analysts made a worse decision based on the data than an outsider would make based on a press release.