The Atari brand has been in so many hands, and been used for so many things (including, most recently, NFTs and hotels) that making sense of it all is maddening. Christ Trotter on the atomicpoet Pleroma instance made a fairly lengthy series of posts laying it all out that, to my eyes, is accurate. He may actually know more about their history than I do, although pride makes me loathe to admit it!
The whole thread is useful, but here’s the first post on it, presented as screenshot because WordPress doesn’t yet support embedding that kind of thing directly. I don’t know why it’s so blurry, that seems to be WordPress again.
Chris Trotter’s Capsule History of Atari (atomicpoet.org, a Pleroma instance)