The majority of players will actually pay nothing at all to play gwent. On the other hand every player has to pay to play Thronebreaker. Thronebreaker targets a much bigger audience than gwent, just check the gogstats and compare Gwent and Thronebreaker. Additionally they sold 50k-100k copies on steam (https://steamspy.com/app/973760). Furthermore the plan was releasing more Witcher Tales if the Thronebreaker sales were good enough.The money printer should be Gwent not Thronebreaker, because you only pay once for TB but double, trice ect for Gwent.
But in the end this all doesn't even matter. You just have to look at the results to see what has been their main foucus.