Real Madrid did not get Mbappe for free; his signing bonus is higher than the amount paid for 99.9% of player transfers. But the fact that Mbappe comes to Real at the right time is 100%, first of all, because Real showed that even without Mbappe they can take all the titles, but Mbappe cannot without Real. That is, this is an ideal situation when the player is maximally interested in proving himself, because if the results with Mbappe are worse (they probably cannot be better), then many will blame him for this.
There's no doubt to the fact that the sign-on fee of Kylian Mbappe is one of the most lucrative in the history of footballers transfer but it doesn't change the fact that he joined Real Madrid on a free transfer. Once a player leaves his club as a free agent and joins another it is recorded that the transfer is free irrespective of the amount that's agreed as he wages or any other offer in his contract. The signing of Kylian Mbappe as a free agent helps Real Madrid to balance their spendings and not break the Financial Fair Play rules after spending huge to land Jude Bellingham last summer.As a Real Madrid fan, I'm extremely happy that the club was able to sign a player they've actually done so many things to bring to the club in the past years. I have no doubt that the Frenchman will succeed in the club by winning many trophies and individual accolades.
And this is a suitable value for a big player, Mbappe, at a big club like Real Madrid.
Source: details of Kylian Mbappé's contract at Real Madrid
And of course, that's not a problem and actually contains benefits for both. In the end, Real Madrid can also allocate these funds to look for other football talents to strengthen the team, both as main players and as substitutes.