Barcelona is currently facing financial crisis, which has led them to explore alternative options. Because of their limited funds, they are offering multiple players in exchange for transfers. As of now, there is no negotiations between Barcelona and Mbappe. It's impossible task for Barcelona to get Mbappe under any circumstances. In this race, Real Madrid choose to remain silent. Despite their silence, yet no offer provoke Mbappe's situation, even a lucrative offer from Saudi Arabia. Without performing actively in transfer market Real Madrid is in a safe zone and favorites enough. Kylian would return to Madrid for free, and he will keep his word.
The economic crisis that Barcelona is currently facing forces them to bring in free transfer players, that is the only alternative that Barcelona can take in order to maintain their finances. Signing Mbappe is definitely impossible, these rumors can never come true. Barcelona of course really want to have a player like Mbappe, but difficult financial conditions have kept Barcelona silent without making any breakthroughs in the conditions that are befalling Mbappe at PSG.
Imo, Real Madrid silence indicates that they have reached an internal agreement with Mbappe side, Mbappe attitude of not wanting to extend his contract with PSG has a relationship with Real Madrid silence. Real Madrid prefers to bring in Mbappe for free rather than having to spend money to make up for Mbappe very expensive release clause.