Real Madrid are the biggest club in the world, there is no doubt about that I think. As big as they are though, they will never get Trent Alexander Arnold to leave Liverpool. He is born and bred in the city, Liverpool is his team.
Besides £70,000,000 wouldn’t even buy his left leg

No way he goes to Real Madrid and I would take bets on that.
Alexander-Arnold is important, though he has his weaknesses and he's probably working on it. Liverpool occupied the englishman with important roles and he's not thinking of exiting Anfield anytime soon, but there are some elite teams that a player can not decline because they're the best club in the world. Real Madrid is an elite team popularly known for the fierce appearance in games and winning major trophies in elite tournaments. Real Madrid are always one step above other opposition, scouting for better replacement for Daniel Carvajal Ramos. Carlo Ancelotti will ensure he's able to sign a prominent player in the coming transfer window.
When the player is under contract with the club, then even if the player does not want to leave but the club wants to sell him, then it will definitely happen transfer. now I also see Arnold is one of the important players for Liverpool and honestly I also see Liverpool will consider with long consideration if then they think of selling him. For now the possibility of him staying at Liverpool is still very large, but when the offer comes and the amount is tempting, then it also does not rule out the possibility of changing their decision in the end, either from the side of the player or the club.