Yes, I'm afraid so. It just goes to show that there are many factors in whether a transfer gets done or not. Objectively, Cucurella will be far more important to Brighton than he'll be to us. For us, he'll be a very useful addition (probably); for them, he's their best player. Unless there's a disastrous drop-off in form, or an injury, they can hold on to him for another year, and probably get the same money.
On the other hand, from his point of view: this opportunity will not come again. We are the best team in the land. This does not really need a lot of discussion. Liverpool are on our heels, but they are not at our level. Does Cucu want to miss this chance? We will almost certainly not wait a year.