This isn't a fake issue - there are users who post occasional high-quality questions, a slew of okay questions, and then several highly problematic ones over the course of their SE career, and they are given the same permissions as a user who steadily posts decent questions/answers and puts in the effort to learn how to post said answers/questions. Time, and the law of averages, is on the former problematic user's side.
But, it is not as severe a problem as this question makes it out to be. As @PatrickHoffman said, a single moderator is moderated by the other moderators and users on the site - they are not subject to exemption from the rules.
And even if they are not the best user, they have proven by merit of their long-standing existence that they are not looking to sabotage the site - whereas a user who posts one very well-received question may have hit a positive nerve on their first try, unlocked a high number of mod tools, but not actually fully understood the nature of SE, and could also become problematic.
In both of these cases - of a user who has been 'rep-inflated' and a user who had a single superstar moment - the balancing factor is the same: moderators who do care and have learned how SE works over the years, and take action accordingly to prevent and mitigate the damage.
And, of course, all the most problematic privileges are locked behind the Moderator Elections, and you can't win those simply by inflating your Rep*.