I think a lot of the parental desire for a trans kid happens because of the notion that it's sort of a rebirth.
You almost never see the Jennings style "push trans on your kid" thing from parents who are planning on having additional kids. It always happens after a family has their last baby. The trooned child isn't always youngest, but the youngest has been born by the time the troonout is announced.
We have a big thing in our culture about pregnancy announcements, gender reveals, name announcements, etc. Combine that with the natural, evolutionary sadness women frequently feel about the end of their childbearing chapter of life, and you have a recipe for women who can't or won't have another baby but still feel a deep desire to experience it all again.
You see some parents of teens who transition say that it's like their child has been replaced, like their child died and this new one took over in their stead, and they grieve the loss. But the Jennings and other similar families feel good about this replacement: Look. a new shiny kid! Let me tell all those pregnant bitches on Facebook and Insta all about their new gender and new name and take new family photos with new special clothes to commemorate how we're changing and growing as a family!
A normal person would be horrified and sad if their 7 year old dog was gone one morning, replaced by a puppy. But we all know someone who would be happy and take a hundred photos of the new puppy and never mention the other dog again, because the novelty is more important than their loyal, boring companion. That's the kind of person who pushes their kid to troonery, complete with media circus.
Jazz was like having a fifth baby. A new gender, a new name announcement, and every transformative surgery its own party and cake and celebration. But now it turns out the fifth baby is a fat girl in a muumuu who writes bad poetry about rainbows and makes ugly craft art.
The Jennings dedicated a lot of time to the Jazz project. Imagine, if they'd applied that time well, how much better a start in life all their children could have had. They threw away the future of their kids in the hope of making them "influencers" in the queer freak show scene.