Why ? Because of Leonardo who is back at General Manager in Paris. Leonardo was here at the beginning of the Qatar era and was highly praised for the job he did at the time. He knows that now that he's back people will expect big signings from him. He has set deLigt as a clear target and I think he'll do whatever it takes to lure him because he will be judged on that. If he succeeds, people will say that he's a genius and that he's really more suited for the job than Antero Henrique, his predecessor, was. He has to make the deal so that everyone starts believing again in the "power" of this club.
PSG is awful choice if you are promising player. It may be perfect destination for proven players like Dani Alves or Angel Di Maria. But if you are Neymar or Mbappe or De Ligt, better play in England, Spain, Germany or Italy than playing among good for nothing teams in France. Ligue 1 is clearly one-team league. The second best team of the league is Lyon and just match the quality of squad, PSG is mile better. Hence, there isn't much exposure in France.
De Ligt has both required skills and time to be named among best defenders of all time. Going to PSG for just some extra money could affect his future in long term. It would be better if he plays for ManU or Barcelona. Considering the old age of Chiellini and Bonucci, even Juventus sounds good option.