I think the main reason was the bad relationship between Laporta and Xavi otherwise he could stay for the next season.
Even Flick was not successful recently and they could have much better coaches instead of him
Xavi was expected to be kicked from Barcelona at any moment especially that few weeks ago he was declared out then resumed... Their might be some misunderstanding and tensions between him and the staff but that was mainly due to the poor results they had and for not winning anything this season.
Yes, maybe they had internal problems which ultimately made the relationship between them not good, so that in the end Xavi had to be the one who was kicked out because of the bad relationship. In fact, if we look at Barcelona's performance, he should still be worthy of being given the opportunity to become coach next season. However, news circulating that there has been an agreement between Barcelona and Flick confirms that Xavi will no longer be part of Barcelona next season.
However, I think Xavi will soon find a new team, because his performance is not bad and even shows something that I think is quite promising. So maybe it won't take long for him to get a new team.
It would be quite difficult for both people to work together if they had a disharmonious relationship, and that's what happened between Xavi and Laporta. One of the things that made Xavi want to leave Barcelona before was because he felt that he did not get full backup from Laporta (including financial support) but for a certain reason Xavi decided to do a U-Turn.
That seems like good news for Barcelona fans because Xavi is still willing to carry out his role but, it turns out there was something that made Laporta furious with Xavi. It seems like Xavi's words are that he feels that Barcelona will not be successful if the same method is used next season, which was the trigger.