@armandalb well that's not quite right.
This booster was never designed to be reusable. From the beginning the plan was for this booster to be lost.
I'm positive SpaceX technicians know why the second stage lost contact. This is just shoddy journalism trying to generate some clickbait saying otherwise.
SpaceX set its goals ahead of time and then they met them. They did exactly what they said they were going to do with this mission, so it is a success, by their own metrics.
Yeah, if there were human astronauts involved it would have been a catastrophe, and because SpaceX was just doing a test flight, that's exactly why there weren't human astronauts involved.
This was only the second test of a new system that everybody knows is still in development.