Only the fittest survives and best earns the most. And we fight to prove we are better than the rest to get promoted (Earn it, not given it).
And plus, average % does not decide the outcome, as the best managers can regularly win against 10%+ quality managers, or even 20%-0+, with superior formation and tactics, along with a better-trained team. Those 140% teams will get drawn to play with assos of similar rating (and you are not playing against those teams in the same draw, let alone those particular 140% asso), so it is puzzling why you feel you need to win against those 140% teams at all.