Mbappe is of course exceptionally good. Real Madrid have a great striker in the person of Benzema. Maybe it even performs better than Mbappe. How would you actually get those 2 to play together? I think Benzema performs so well because he has a free role, when Ronaldo was there it wasn't. If Mbappe had gone to Real Madrid, it would presumably be at the expense of Benzema. 1 top striker is enough, and you don't want to put 1 of the 2 on the reserve bench.
Actually there is no problem with that kind of thing if Mbappe really wants to join considering there are so many options that Madrid do in strategy especially for 4-3-3 but right now Mbappe doesn't want to be reported with this Madrid and gets a big advantage at PSG which makes this be complicated for Madrid.
They now need to find a new one because even though Benzema is really sharp this season but we can't guarantee good things next season especially for Madrid itself in this case Benzema is a reference it will be very difficult if Benzema doesn't play well next season