I don't think anyone at Saints screwed up. It's just very hard to operate a 1/3 the wage budget of some other teams. And the number of players and managers we have lost to other clubs. It's especially hard when you try to punch well above your level. Those years we were chasing Europe competition, we could have settled for 10th and brought some young players into the team. That might have made losing the star players less.
I think most likely we were clever and forward thinking as far as scouting and academy and maybe some other things. But then the other teams figured it out, and once they applied their much greater resources to the same strategies we were using, then our advantage was lost.
In the end, it's all about spending. So if you want to blame someone, blame KL. Although that seems unfair as well as without her and her father the club might not even exist today.
The specific screw up i'm referring to is getting rid of an experienced and competent if somewhat steady and safe manager and replacing him with a novice whose only experience was one season at a small club in Spain. It was and has proved to be a gamble that has backfired and one the was wholly unnecessary to take.