Sporting and Newcastle both aren't satisfied with this situation for sure. But I think we should understand the players' future plans as well. They didn't want to waste their time in a smaller team for longer.
Gyökeres is 27 and Isak is 25 now. They are both in their most productive age range. It is better for them to show their skills to the world at bigger teams playing in the most prestigious leagues.
There must be some understanding from the club as well when a player wants to leave. Why? Because while there is a contract, many teams do sell players, because they do not want the player anymore and while some players wait until their contract ends and do not accept being sold (like how Newcastle and sporting refused) but most of the time players who wants to be sold, ends up getting sold and they just accept the reality and move to another club.Gyökeres is 27 and Isak is 25 now. They are both in their most productive age range. It is better for them to show their skills to the world at bigger teams playing in the most prestigious leagues.
So if a team can sell a player, even though under contract, then player could want to be sold, even if they are under contract as well. Isak could request to be transferred, there is nothing wrong with that. A deal is a deal and if Newcastle doesn't want to sell for cheap, they have that right, but that doesn't mean Isak has to accept it and shut up, he could try his best to leave too, both sides are right.