> You kind of did that to yourself if you let the new person get away with it.

In theory, sure, but in practice, to echo the others, you often don't have a choice, because of power dynamics/politics.

Its easy to say "its management's fault", but the principle is the same - these guys are spammers and quacks (and deserve nothing less than to be confined to the level of hell reserved for spammers), they just have to spam long enough and something will get through (volume over quality). And after their "success" i.e. fraud, they can ditch the company and move onto the next. I've seen multiple "seniors" like this, not actually very good at the work, but great at pushing half-baked slop.