Yes, this is a pretty interesting could-have-been to hear about.
The source post did not elaborate on this one, so we don't know if it was actually a serious Lego-Firaxis collaboration, though it most likely was.
We only
know from the surrounding games that the data should date to circa
2017 (Switch launch year, release of Splatoon 2 & Rime; the other canceled titles were in development around the period).
Like Lego Horizon Adventures - the Lego-ified version of Horizon: Zero Dawn, Lego Group could have
approached Firaxis for the collaboration, but Firaxis still had to design and implement the actual game.
And that raises the question: who were its designers?
For example, Sid hadn't been the lead designer in another released game since 2015's Starships, and the last time he tried to lead a Civ game (not counting the social game CivWorld, which had different mechanics) was the earlier CivRev2 with
aliens, Atlantis & zombies, canceled around 2010~2011. Could this Lego Civ be his other shot at making a lighthearted Civ spinoff with new ideas?