From people who want to pretend that hired help is the equivalent of family. It's not true.
But I agree that older people can be effective parents. Although women cannot normally give birth in old age (and the fact that technology could allow this woman to incubate someone else's baby does not make it anything other than insane) men can certainly become fathers at any age, with younger women.
Or older couples can be adoptive parents, foster parents, rear grandchildren, etc. It's up to them to evaluate their ability to care for children.
However, we're not talking, in this particular case, about reasonable people rationally evaluating children's needs and the adults' fitness to meet them. We're talking about insanity.
There is no "normal." What's the old line from "The Shadow"? "Who knows what lurks in the (something something)?" So it's not a decision (what we deem) a rational person would make. No doubt--especially if she has the stamina--adopting would have made more "sense"--especially in the many years that led to this. But I don't see this as "insane." Stupid? Maybe.