Bombing as I understand relates to sales exclusively, like I have already explained: a controversial movie with an audience split in half which earns a lot of money isn't considered a bomb, but a critically acclaimed universally beloved movie which earns too little money - is. And like several people told, the problem with civ6-7 steam player count comparision is the fact civ7 got released on many more platforms than civ6 did, so until Firaxis reveals the actual multiplatform sales figures we can't say anything concrete.
I've just checked wiki. Civilization VI released only on Windows (Steam only) and macOS, with other ports coming slowly over the years or never at all. Civilization VII released simultaneously on Windows (Steam), macOS, Linux, Nintendo Switch, PlayStation 4, PlayStation 5, Xbox One, Steam Deck, and Xbox Series X/S AND last but not least on Windows but on Epic Games Store instead of Steam (EGS only came around in 2018).
It is hard for me to imagine that the total sales wouldn't have been massively increased by... you know... factoring in all those SEVEN MORE platforms mentioned above (ignoring Steam Deck for obvious reasons).