1. They realized just owning the software platform is very limiting (For example they can't compete with Apple no matter how good they are. Just look at Google maps. Thousand times better than the default Apple maps but will never be #1 map app on iOS because people always choose the default). Also, now even Google is moving towards owning their own hardware platform. As a VC funded company I think this is the best timing to exit. Otherwise it's all downhill from here.
2. Samsung wants to fight with Google/Apple/Amazon/MS and needed a weapon (because, you know, people say AI is the future nowadays).
So at best these guys will be integrated into Samsung phones to differentiate Samsung's hardware. I don't see them becoming the "open platform" that they envisioned at all.