Barcelona decided that enough was enough when they saw that the overall sum to bring in De Ligt would surpass 200 million euros. The estimated transfer with Ajax would cost 75m euros plus add-ons, and the centre-back would sign a five-year contract. Having asked for 12m euros net per year, it would cost the club 120m euros in that period just for his salary.
Between the transfer fee and his wages, the overall deal would cost more than 200m, and that is forgetting one last expense: Mino Raiola's 20 percent commission from the transfer fee.
Barcelona stood up and said no. They were not willing to make that expense for a 19-year-old, and it would have completely unbalanced the club's wage structure.
https://www.marca.com/en/football/barcelona/2019/06/22/5d0e4354e2704e7a718b45b2.html
Apparently he chose Juventus because the French league isn't competitive enough and ManU can't offer CL football.