There’s nothing in it for anyone else.
Although I'm a little worried about driver performance, especially in cases when there's just ~100 microseconds time for the driver to react.
Giving Android away to OEMs is in large part a vector to get the Play store, Chrome, Maps, and their monetizable services and data scarfing on the device.
But some OEMs don't bundle everything. Think of the de-Googled Android variant ran by the Kindle Fire series, or the Chinese phones that include local stores and service providers that work there instead. Google can try to bludgeon them into playing ball with the trademark and various over-the-top agreements, but they can't stop them from saying "We'll take AOSP and make our own version and call it FireOS."
With full licensing control up and down the stack, they can close that door much tighter.
Also, similarly to Apple, GCC just got removed from Android.
Only the kernel is left.
Reading between the lines of some Joe Duffy posts, I think Midori was a victim of rise to power from WinDev after that whole Longhorn/Vista history, only to end with UWP slowly getting back all the .NET features that they decided to throw away on the initial version of WinRT.
Apparently post .NET Core 3.0 there will be some changes happening to .NET Native. It was briefly mentioned at Connect 2018, but they didn't wanted to precise what exactly.
I don't think it's fair to say Kernel research is a thing of the past.