It is by design. Having low rated players allows him to get easier draws for Cup and League. If you ask him, he will say he does it all to win the Cup, and that the League is like a playground. His dominance may upset you, but he is not thinking about you, he is thinking about the Cup, Or perhaps he is thinking about winning the trifecta (League + Cup + CL), known as the "treble" around here.
This method of artificially lowering the average quality of the entire squad (or the top 14 as far as Cup is concerned) is well documented, much discussed and generally accepted by most managers at higher levels as the necessary evil if one is to be competitive in the Cup. I really do believe it is an example of a prisoner's dilemma. Everyone would be better off if no one used this method, but everyone is better off personally using it.
One thing I doubt is that the manager in question has money to burn. Assuming the low rated players come from his academy, they all have Russian names (except for one). That would make him Russian. Unless he just likes Russia and Russian soccer (now there is a joke!). If he is Russian, he is likely to have more time and technical skills that money. He is probably farming for tokens and boosters, either legitimately or with a hack.
As an American friend of mine says, if you are not cheating, you are not trying. I am surprised Russians did not come up with this saying, because it is pretty much their life's philosophy.