OP is talking about the first Baldur’s Gate game. Not Baldur’s Gate 3 which you are talking about. Also Baldur’s Gate 3 was in production in 2017. While it may have been in response to Stranger Things season 1 coming out, I honestly doubt it was that. BG3 is a huge labor of love and that dev team was much more intent on making a good game than cashing in on popularity of any particular ttrpg system. There are no dlc or micro transactions and marketing was sparse. I pretty much only heard about it through word of mouth. If the goal was to capitalize, they failed that. You don’t capitalize by making a game that people can buy once and have nearly limitless experiences in without spending a dime more.