This expression of "they" is, on the one hand, no more than a turn of phrase, a pronoun intended to express a collectivized concept of the power-brokers (politicians, banksters, etc.) one comes to recognize as the parts of an oppressive and corrupt system. On the other hand, this formulation of "they" illuminates an image of the oppressive system as a kind of cloak and dagger organization, something like a demonic cult or twisted college fraternity that sets out to destroy the world.
The latter of these two is potentially the more naive (and dangerous), given that it grants a monolithic status, an organizational capacity, and a unified will that "they" simply do not possess. However, it must also be admitted that both these conceptions of the "they" function to exonerate "us" from responsibility for the perceived ill, given that it is "they" who robbed, pillaged, and corrupted.
Let us take as an example the Canadian robocalls scandal. The Canadian public has some evidence as to who should be held responsible for defrauding our democratic system in this instance, yet all the names have not been named, and the entire sordid affair remains in the realm of the yet to be revealed conspiracy. Simply because the public is not in a position to identify all of the culprits by name is no reason to say that "they" (whomever they are) are not responsible. "They" most certainly are responsible, and "they" must be brought to justice. But what is avoided here, through the formulation of "they", is the fact that it was "us", all of "us", who allowed this debacle to take place at all.
Wishing to say more with less, let us leave off here with a few words from the film adaptation of Alan Moore's V for Vendetta (followed by a short clip), which puts forward, in some respects, a more pragmatic understanding of the "they" while also embracing the responsibility of "us":
"Certainly there are those who are more responsible than others, and they will be held accountable. But again, truth be told, if you're looking for the guilty you need only look into a mirror."