To get to where we were, 3 short days ago doesn't happen overnight, but also a big part of our failings (in my opinion), has been not understanding the need for big clubs to have at least 2 or 3 big players. Liverpool might just find that out.
Big teams need players who get into your PL squad of the season, and probably at least 1 who gets into the starting 11. Look at that Leicester, PL winning side, and then....
Culture, as you describe it matters, and that's why the likes of Bournemouth, Brighton, and to a large extent Palace delivered, although in the case of Palace, back to my first paragraph.
De Zerbi's challenge, on the pitch is probably going to be to create a team who are competitive without a top player. Once, and if he does that, then we try and capture better players.
Without the injuries last srason we finish mid-table, but it would not have solved the problem.
Someone needs to see both needs.