He has just renewd few weeks ago.
Also, he has the same agent as Pedri and Torres. This could mean previous links was agent favour, or they offered him to us.
Same way that now we are linked to their own client, Rodrigo Mendoza
His main issue is that Villarreal still holds a buyback option, and apparently a portion of any future sale. This makes less incentive to sell him for Rayo. He is their best player and selling him won't compensate them well.
However, at 28 (next summer) it will likely be the last transfer window they can get an 8 figure deal for him. So, they might decide to cash for highest bid, which is likely be around 15M or so.