In this particular case, I think it's very specific to Jamstack, but the point behind people adopting it is strongly connected to developer preference.

I think a lot of developers are keen on working with new frameworks, that are easier to use and extend for a developer, but they don't consider how easy the end product will be to use and maintain by the end-user.

Overall, I think WordPress is the best software I have ever seen in terms of usability and has a good balance between customizability and how easy it is to just quickly build something. But developers tend to choose the stack, and its easier for them to overlook the maintenance part.

I think for certain situations Jamstack might be better. But the majority of WordPress admins, probably don't want to write articles in markdown.