Selling players to your competitors seems like a dumb idea.Couldn't they just sell Dybala to a non-Italian team?
Dybala wasn't sold. His contract expires at the end of the season and after that he becomes a free agent. He is free to go wherever he wants. The contract couldn't have been extended because Dybala requested too high of a salary. Someone might say that the club could have given him the wages he requested and then sell him. But that creates other problems. He isn't playing at his best and it would be difficult to find a club willing to offer him the same (or better) financial terms. And Juventus would be stuck paying too high wages. Something similar is happening with Alex Sandro, for example. The guy is basically retarded, but not even weaker clubs want him because he earns too much.
Dybala should definitely be resigned if they could. Juventus needs him badly, they do not have any players who are that good right now. Even if they can't keep him, at least sell him to another team for a good amount of money.
If they end up losing him for free, then they will regret that, he is at least a 70-80 million euro player if not more, and losing him would cause them to miss out on that much money, or a player that they could keep and provide a ton of goals and assists every year. Pay him whatever he wants, only because he can't be replaced, you can pay less for another player and will not get the same results as he could provide for you.
But basically Juventus have got a replacement and that is Dusan Vlahovic, but I personally am not too happy for Dybala to choose Inter as a runaway. Because if he is free to choose, at least Dybala can have access to other leagues such as EPL, Bundesliga, La Liga and Ligue 1. Indeed, Dybala chooses a team that can pay him and the chosen team at least plays for the Champions League too. But if there are still teams outside of Serie A who meet the criteria and are able to fulfill Dybala's wishes, then it will be better for Dybala and fans will still respect him but unfortunately, Dyabala chose a rival team.