Not all of the players who forced their transfers were disrespectful to their clubs without a trigger; the clubs may have dishonored a deal or arrangement they made earlier. In some cases, the buyout clause will be met, and the new club that the player wishes to join is very willing to pay up, but their clubs make the process difficult, stalling the deal so it can fail when these things were discussed before and that was the reason the buyout clause was set.
So yes, there is a contract, but also in the contract a buyout agreement is detailed.
Compete different situations with the Isak, Wissa and Guehi tbh.
I just went back to see the contract agreement between players like Isak, Wisaa, and Guehi and their former clubs, and yes, there was no release clause in their contracts. So I now understand. Their clubs completely have or had the right to act in any manner they want. The players were wrong and disrespectful to force their move.
But for players like Gyokores, who forced his move, it was the club trying to disrespect him and their agreement when he clearly had a buyout clause and Arsenal was ready to meet it, but the club wanted to use technicalities to not honor the clause. You cannot fault players in such a situation for their actions, but the club.