Williams himself wants to play in Barcelona and even agrees to receive a not too large salary (which will still be higher than in Bilbao) so that Barca can afford to have him on their roster.
I don't believe Williams will escape the temptation of money. If he leaves Bilbao to play for Barcelona, it could happen, because after all, Barcelona is still a better place for him to develop his career. But if other big teams offered and paid high salaries, I don't believe Williams would still choose Barcelona. For example, PSG, Man City vs Arsenal offered to recruit him. You said that Williams would choose a financially strong team or still choose a team in a financial crisis like Barcelona.
But as I already wrote at the moment, this is not the main thing, since if the compensation under the contract is large, then everything is in the hands of Bilbao and they can demand either the entire amount due for the premature termination of the contract or negotiate on the terms that suit them.
Currently, Williams is still bound to Bilbao until 2027 and has a contracc-breaking fee of somewhere 58 million euros. This number does not face many obstacles in activating the clause to break Williams' contract. The important thing is, is Williams' talent enough to attract big teams? If enough, Bilbao will have difficulty keeping Williams.
https://www.90min.com/does-nico-williams-have-release-clause