I think Arnold should take a huge credit. When Woodward was at the helm it seemed like he was content with following the whims of the manager and mostly disregarded the footballing/scouting side of things. As
@Adnan has stated many times, Ole and Mourinho used to use their own personal scouts for instance instead of relying on the whole team. Under Arnold it seems like they (Arnold, Murtough, and Ten Hag) have formed a team and are working in harmony, which is exactly what is needed. There's no other big club around who indulged their managers like we did.
The big difference here however is, unlike under other managers our players actually improved as the season went on. For instance, I remember when Darmian came into the team he played very well and it looked like we had signed a great player. But, as the season went on he declined further and further, or similarly Schneiderlin who was the same. There are numerous other examples. Di Maria, Pogba, Mkhitaryan, Bailly, Lukaku, Maguire, AWB (improved last season though) etc.