Liverpool management might not hire Xavi because he can't coach and lead his former team Barcelona to victory. How can he lead Liverpool to victory in a tough and competitive League like the Premier League?
If Klopp leaves, Alonso or De Zarbi will be his perfect replacement if they agree to change teams, but others will just come and give it a try. In fact, Liverpool's performance will drop as it will take time before they recover.
You first say that he couldn't succeed in Barcelona because of financial troubles there and then you say that he couldn't succeed because he wasn't coaching the team well enough. Well, if your first point is true then there is nothing a coach can do about it and hence it wouldn't have an impact on Liverpool's decision to hire him or not. Because if Liverpool has the money, Xavi could do a good job.
But I think that your second point is more true than the first. It's correct that Barcelona has financial troubles, but Xavi is an overrated coach who doesn't understand how to improve players and how to promote the younger talents and give them the right advice and coaching support to make them play on their highest level possible.
I would be shocked if Liverpool were to decide to sign someone like Xavi. It would be disrespectful towards Klopp, who was a great coach with skill and passion. Xavi doesn't have the skill.