I'd assume it says quite a bit more about Game Pass adoption than the FH brand itself, but good for the game nonetheless.
EDIT: As I'm getting quoted in so many posts, I'll clarify that I'm talking about the growth from 4 to 5, not the sheer number of players. Of course FH is a big brand, but I'm saying that the delta between both games is probably closely related to the ecosystem and its evolution those past 3 years.
No need to be so defensive and trollish about it. I'm level 77 in the game currently and have purchased the premium add-on to play early, so it's not like I want to diss the game in any form.