It hasn’t. Unless, I’m really misunderstanding. Hack means someone who is in the industry, usually a service industry, and has been doing the same thing a long time, and some people associate it with an industry that doesn’t take much skill, but still the person doing it knows the job well.
Like a taxi driver has a “hack’s license” in NYC.
Or, someone can be “hacking around” or “hack around.” Meaning not accomplishing much but spending time doing something anyway.
I guess it’s sort of similar to monger, but hack is probably slang (maybe monger is too? I don’t know) and monger usually refers to selling an item rather than a service.
In your examples it’s like saying cooking pros, but instead of saying pro, the nice word for someone who might be well trained or educated on the subject, they use cooking hacks, which I would take to mean they might be well trained, might not, but they know the topic inside and out by doing.