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.
Real Madrid is the best team in La Liga and everyone knows that with full clarity. Real Madrid will do extremely better next season, always ready for the fierce competition and will do everything within their reach to ensure they're hitting upon the big winnings. Kylian Mbappe is signed by Florentino Pérez and Carlo Ancelotti, he's here to do what he does best.
Saying Real madrid is the best team in Laliga is an underestimation, they are probably the best in the world right now. It's not because they have won the highest number of champions league or domestic league but because of the performance they display whenever they play games. They play collectively and not relying on a single player. We thought the team performance will depreciate after Ronaldo left, the same thing when Benzema left but surprisingly, the young players currently in the team make it to be more stronger than it was before during the era of their legends who left. They recently signed Mbappe finally after rumors for several months now, it's indeed an addition to Real madrid and will continue to dominate football for seasons to come.