Mediocrity is an overestimate, mediocre is managing bottom table EPL teams. They'll fade into obscurity, quietly hushed and thrown as Pundits.
For me football is many simple things done right. Passing, trapping the ball, dribbling, feint, only when this basics are drilled correctly in everyday training will a player improve. It's not magic, Klopp/Pep prepares their team meticulously to atomic levels, they even analyzed which opponent is playing and how to specifically counter him. Which side should they push from, who's better to cover who, show weaker foot, etc.
For top teams, the who, what, what, when, where, how isn't a coincidence. What we saw as telepathic understanding isn't magic, it's a result of a move set being drilled over and over again in the training. I read somewhere that Pep was so meticulous that like a brain surgeon he told his players to cut their reactive movement to improve their off the ball movement. Small little things even the player didn't realize such as the tendency to tap the ball twice before passing, or the tendency to take extra tap while dribbling. Do we honestly see ole as this kind of person? The 3 of them sits in slump on the dugout, they never actually analyze the match, they never bark instructions, they never take notes, as if they don't know what's happening
Bottom line is that high level team has high level coach, that does much much more than a simple "you play here, pass to x, make forwards runs, go and have fun"