This is an interesting topic of "whose to blame". Like in all aspects of society, I think we can't place blame entirely on the system, nor on those who play the game within it.
For example take the US housing market bubble that bust and triggered a world wide financial crisis. Now here is a case for which, yes, the lenders were practicing a type of high risk financing that no healthy economy should permit itself, though at the same time, the buyers were all too easily persuaded of a materialism that says they should have something more extravagant than what their real earnings would not otherwise consent.
In our case, the cyclist is certainly the one in the long chain of responsibility that usually takes the brunt of the consequences when caught in flagrante (as also happened to home owners when compared to many of the banks). And is certainly faced with a load of pressure to do what must be done to survive in this profession. For this reason, I can understand the aspect of being the victim of corrupt and illicit system that is more powerful than individuals.
However, and this is a big however, the truth is also that many cyclists, and athletes in general, are types with little moral character and because of their own narcissism, megalomania and ruthlessness are quite willing participants in the doping process.
I have been around many cyclists quite like this, who needed little prompting from the rotten system to dope and were actually quite smug and arrogant about it.
Bottom line is that this is a complex issue, as is anything of a moral and psychological nature, that can't be either superficially or universally explained for all cases. Consequently if it is true that cyclists face many pressures from a system that literally holds their jobs and very lifestyle in an extremely fragile state of certainty while they ride professionally, it is equally factual that many cyclists are morally jerk-offs. Not all of course, though probably not few either. While most certainly aren't innocent lambs either.