Yeah De Zerbi is another candidate who might be a good replacement. I said Xavi because of thinking that he isn't actually a bad manager. He has managed Barcelona for less than 3 years time so he isn't very experienced.

However Xavi looks like a manager who knows how to work with young talents. He is giving the chances they need for their development. Besides Barcelona actually got a La Liga and Super Cup titles in the previous season. This season wasn't good enough but there are always ups and downs for most teams.  

Anyways, when it comes to the reason of Pochettino's sacking it is hard to tell. It was a meaningless decision of the chairman.