The number 3, 4, and 5 contributors to SvelteKit in the past year work at Vercel: https://github.com/sveltejs/kit/graphs/contributors?from=8%2...

Rich and Simon are incredibly important, but they're in it for Svelte and the community more so than a paycheck from Vercel. Tee has been doing most of the maintenance on SvelteKit currently funded by community donations. And this isn't counting other infrastructure like vite-plugin-svelte or the Svelte CLI which are entirely maintained by volunteers. I don't think Vercel funds a majority of the work on Svelte even if it might be close to it.