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.
No buyout clause in Ghehi or Isak's contract, the only clause Chelsea included in Ghehi's contract was " Matching clause" meaning if crystal Palace agrees a deal of €38m with Liverpool, Chelsea can match the same deal and take the player, it's called a right of first refusal. We also have a 20% sell -on-clause in his contract.
The club will always be bigger than the players, don't let the media gaslight you.