Without something overt, like a note left behind or friends/family noting such tendencies, I’d be real hesitant about jumping to conclusions.
In the first place, a loss of directional control during landing is a significant factor in aircraft accidents, especially with taildragger aircraft. I don’t have figures for J-3s, but about 9% of all homebuilt accidents involve the pilot losing control on landing. Roughly the same as accidents involving inadvertent stalls.
It doesn’t have to be pilot-induced, either. Loss of a rudder cable, loss of a brake, loss of a tailwheel spring, breaking a horn on the rudder can all lead to the loss of directional control.
Arthur’s suggestion that his leg/hip injuries may have affected his control were spot-on. I had a knee injury earlier this year…was better, then it flared up big time while I was flying a couple of months back. I had trouble keeping my little taildragger tracking straight after a touch-and-go; my left leg was nearly numb. Went back up and let it calm down.
Finally, let’s look at the logic behind deciding to deliberately set up such a crash. Note that as a race driver, he undoubtedly had a good working understanding of physics. He was flying a J-3 Cub…relatively slow speed. I assume he was flying from the rear seat, which means he had plenty of crush space in front of him. But in that crush space was the fuselage-mounted fuel tank.
The odds are, the plane wouldn’t have hit the barn hard enough to instantaneously kill him. He would have understood that. But he probably would also have understood that there was a high probability that the fuel tank would be compromised, spilling fuel on the hot engine and the wooden side of the barn. And, even if not knocked unconscious, he probably would be injured badly enough to make it difficult to extract himself from the wreck before the gas-fueled flames took over.
In short, it was a perfect setup for burning alive. Do folks really think he deliberately chose that? Plenty of other ways to deliberately crash that would provide a more-sure solution.