Harry Kane would be a good choice to replace Benzema, but Real Madrid may have put all their efforts into preparing for a super blockbuster transfer to bring Mbappe to the Santiago Bernabeu. This is a perfect alternative that couldn't be better. Mbappe can bring the royal team Real Madrid back to the era of European dominance, just like Cristiano Ronaldo did.
Kane is being chased by Munich and United. He still doesn't want to extend his contract with Tottenham. although the coach still really wants him to stay in the team. which is why it will be difficult to get Kane in the transfer market this summer for Madrid.
Similar reasons may be faced when Madrid wants to sign Mbappe. their club actually doesn't want to let go of players and that's what makes the price the club wants very expensive. but if PSG and Tottenham do not release players in the transfer market this summer, of course, there will be losses for the club. they have to come to an agreement before their contract is finished. It is clear Madrid needs one of them to make this season easy for them. I'm sure the competition with Barcelona will not be easy for Madrid this season.