We were second last season with almost exactly the same team bar Suarez - did any of our players meet the requirement of being good enough to get in another top four team back then? Of course not, because there are so many other factors that are equally as important as the quality of your players. United was seventh last year and got top four this year while the majority of the players was the same. It wasn't the quality of your players that was different this year, it was your manager and style of play.How? When your goal is to get in the top 4, it's going to be very difficult to do if hardly any of your players are good enough to get into their teams.
Those two plus confidence, character, leadership, ... are all necesarry ingredients for a team to succeed. How many Atletico players would've gotten into Real's or Barca's team last year? It's the team as a whole and all the surrounding circumstances that counts, not the individual quality of the players. Sure, it helps if they're very good players, but that doesn't garantuee you anything.