Being a free agent at the age of 25 with a good statistical record with Lille, I don't know why Lille didn't extend his contract before this happened. However now Juventus has officially become the winning team in the hunt for Jonatan David's signature and gave a contract of approximately 5 years if I'm not mistaken. Quite a smart investment from Juventus.
Jonathan David himself does not want to accept Lille's new contract offer because he intends to leave and play for a bigger club even though Lille themselves have tried to persuade him. It is impossible for a club not to want to extend the contract of a player who has great potential like him but they also cannot force it because his contract ends this season.
Juventus is very profitable in getting Jonathan David because previously Napoli themselves were also quite interested in the player. The success of the approach made by Juventus will make their attack line next season better because of the impressive performance he showed last season with Lille.