Mbappe chose the money instead of having a better career. I don't mean that his career is bad now of course. Maybe PSG haven't been amazing in the Champions League so far but Mbappe has still been showing a wonderful performance. He is the most important player for his team now undoubtedly. So it isn't too difficult to understand the reason why PSG were ready to pour an incredibly high amount of money to extend his contract. But I believe he can have a better career if he joins Real Madrid later. Real Madrid are a winner team while PSG aren't. I don't mean the domestic leagues of course. 
Nobody knows Mbappe fate, but usually when a footballer is after money over quality, the story doesn't go far. What's so special about Mbappe in the eyes of PSG? Or is it just PSG's ambition that wants their club to be filled with stars? They failed to even reach the Champions League final. Even when Messi was at Barcelona, we never heard that a player's position could exceed the club itself. Ronaldo when he was at Real Madrid could not exceed the position of the club. Now we see Mbappe who is still young, the quality and achievements he gets are still below Messi and Ronaldo, even as if he is the world's number one player in the eyes of PSG. it's ridiculous
Nobody would like to underestimate Mbappe in any way for sure. However I don't see him as the number one player when we take Messi and Ronaldo's primes into account. I'm not a PSG fan but I wouldn't still say so even if I was a PSG fan. It is the truth that Mbappe is still very young and he has long years ahead of him to improve himself even more. I guess that he needs to leave PSG and join a team like Real Madrid to get close to being the "number one" in the future. PSG don't seem like they will have a very bright future full of titles except the Ligue 1.