De Ligt is not in Alderweireld's league, granted he may be one day. And I can understand the links, that Ajax-Tottenham jewish connection, a lot of ex Ajax players at Tottenham including a former team mate Sanchez. Pochettino who will put faith in young players, and a path to the first team. Sanchez practically walked into the Spurs starting 11. Look at Spurs' CB's, Vertonghen, Sanchez, Foyth, Dier, the only experienced CB they have who is a shoe in to start is Vertonghen. Sanchez did well but still young, Foyth barely played a game in PL, Dier is a utility player who can play CB in a pinch. De Ligt might see Spurs as a good move, where the path to first team football is easily achievable compared to some of the European giants. Whilst still being at a club with CL football and all the bells and whistles.
The Dembele move is understandable from the players perspective. His body just cannot take the rigors of playing so many games in a very physical league. So he has to look at his alternatives, taking a role on the bench as more a squad player or moving abroad for a big money payout to China. Im sure if he does elect to move on he will have the clubs backing and Spurs will be suitably reimbursed for his services.