GitHub has been investing in React for a while (e.g. see our accessible React design system https://primer.style/react/). Many developers at GitHub have experience with React, which helps. And the tooling is just more mature (IMO)
Marko is tailored for that. Solid has mostly focused on highly interactive SPAs until very recently. Solid’s creator also worked on Marko and has written a lot on the subject. But even so he mostly deferred to Astro for mostly static use cases with Solid until the most recent release (Solid/SolidStart) officially supported partial hydration.
