But, that's the point we keep trying to get across. The ONLY reason the players could decide to go north to Fire God's Mountain is because, you, the DM, put that there as a potential destination. Same as Shrilly Vanilli (I am SO stealing that name for an NPC btw). How did they meet someone halfway through their journey? Who added that NPC? Did the players request or take some sort of proactive action to meet this NPC? No. You added it as the DM. And, guess what? There's going to be something interesting to do at those locations. Imagine that. How did I, who isn't even in the game, who has no idea about any of the details of your game, able to predict that with 100% certainty?
Well, because I know that we're playing a game and it's your job as the DM to make sure that there actually IS something interesting to do everywhere the players go. So, no, the player don't have any real control here. Not really. Their only real control is choosing from the list of options that the DM has provided. Had there not been an NPC that you, the DM, added, they would not have gone to Shrilly Vanilli because they would have had no reason to go there. Where did that reason come from? From you, the DM. You weren't "reacting" to anything the players were doing. You were adding stuff that you thought was interesting.
Which is fantastic DMing. That's what you're SUPPOSED to do. But, at not point should we be kidding ourselves that this is somehow the players being proactive or you are doing things "in response to what they are doing". The DM is very, very firmly in the driver's seat and the players are along for the ride.