TGL seems like an attempt to bring the traditional live sports model to golf. One in which you have as set arena, with numbered seats for sale, and you can charge a premium depending on proximity to the players. Golf is traditionally not a great live sport simply because the action his happening in multiple locations (except in match play, but lord knows TV ended that) thus it is impossible to maximize revenues by capturing the consumer surplus, because they cannot charge variable prices.
It also seems to be an attempt to capture some for the video game streaming market (currently approx $9B). I know it seems crazy, but video game streaming actually has become an extremely profitable industry.
I'll be honest that I cannot imagine myself watching (I pretty much only watch majors at courses I care about anyway), but this seems like a very reasonable bet to me considering how small of a market they need to make it profitable. Four-player teams, at small, live venues, plus streaming will likely not need a large audience to succeed, especially with a very young audience they can later convert into PGA Tour fans.