These grants are competitively reviewed by experts in their fields, and are quite hard to get. Even twenty years ago getting an NIH R01 was considered an important career accomplishment.
Now, as to the topics being funded, the broad strokes are set by Congress, which is why much of the funding goes to medical research since pretty much everyone likes the idea of better treatments for things like cancer or Alzheimer’s disease. If there was an entire field they considered unnecessary, the legal process would be working with Congress to either remove it entirely or put in restrictions. They aren’t doing that, of course, because that would force people to actually go on the record voting for something specific and that usually exposes that “junk science” claims are deceptive.
Now, as to the topics being funded, the broad strokes are set by Congress, which is why much of the funding goes to medical research since pretty much everyone likes the idea of better treatments for things like cancer or Alzheimer’s disease. If there was an entire field they considered unnecessary, the legal process would be working with Congress to either remove it entirely or put in restrictions. They aren’t doing that, of course, because that would force people to actually go on the record voting for something specific and that usually exposes that “junk science” claims are deceptive.