Among many other things, they built a system that can provide substantially better concurrency and a better async story.

Also, they're building a project that's more open to outsiders.

They were aiming for better concurrency, I believe. If you're rewriting something regardless, might as well use a more modern language that's easier to reason about during development.

That's how you push the field forward. Good isn't good enough.

If yiu had the resources/time, why wouldn't you challenge or improve status quo?

Sqlite is excellent but I still have many gripes with it, especially around defaults.

I think Richard Hipp has quipped “if you think you can build a better SQLite by god you’re welcome to try!”

Best tested..? The test data/suite is private. That alone is quite odd.

The Rust rewrite? I had the same question.

It’s fast, with unparalleled stability, arguably better managed than any other software on earth, deployed on literally everything, so let’s… fork it for street cred?

Another way of describing Turso is a SQLite-compatible (same file format and C API) embedded database. If you start with SQLite but find you need async i/o, concurrent writers, and local replicas then Turso is a good option.

Because they wanted something like this story to happen. It's what VC does to open source, they aren't here to help or build communities they are here to make money. Nothing else matters.