I think SPA tooling solves a composability issue that people didn't realize they had, and so SPAs are used in a lot of instances where MPAs make way more sense and would be more performant, because the developers want to utilize the composability of components. The fact that SSR is a feature for React and Vue makes me think a lot of projects were really just aching for composability, not interactivity and dynamic data features of SPAs.

A think a lot of backend frameworks offer some attempts at frontend composability on the serverside but it's usually not the same approach that SPA tooling uses. I would love to get people's thoughts on backend tooling that is attempting to solve composability in a serious way, not just tacked onto an existing MVC framework.