RV's can be quite noisy and to a non-aviation person would indeed sound rough. A witness said the pilot was trying to re-start the engine as it flew overhead; does that mean it was stopped and he heard the starter motor, or does he mean it was spluttering or idling and the throttle was being manipulated? If we knew that, we would have an idea, but we don't.
What is concerning is the lack of survivability in an almost intact cabin area.
I can answer your concerns with a question. What happened to the landing gear? Why is the fence in-tact just behind the aircraft? It's because there was little to no forward speed. It's clear from the picture that to an extent, it pancaked in.