No matter the competition, the object is to win.
Yes with the G-League the goal for many of the players is to showcase their talents to one day get called up to the NBA for a long-term contract. The NBA teams view it as a bit of an incubator too, sending their young players to get playing time they might not get on the main roster.
The coaches are balancing this too.
They are trying to mold their team to win while at the same time giving their players a chance to shine. And then at the same time trying to run things in a way that theoretically will keep their players ready to play for the parent club when — or should — they call.