Many years ago, when American riders first burst onto the roadracing scene, and immediately dominated Grand Prix racing, dirt track racing was seen as a key part of their success.
Training on the hardpacked dirt, where pushrod twins have far more power than they can ever transfer directly into drive, translated very well into racing 500cc two strokes, which had the same excess of power over grip.
As tire technology advanced, and as the number of racers coming out of the US to race on the world stage declined, dirt track fell out of favor. Styles changed back towards keeping the wheels in line and carrying as much corner speed as possible, a skill learned in 125s and 250s, and taken up to 500s and MotoGP.
The advent of the 800cc bikes, which caused a quantum leap forward in electronic control, emphasized this even further.
The dirt track mindset had not disappeared completely: both Casey Stoner and Nicky Hayden cut their teeth racing on the dirt, and carried that style into MotoGP. Hayden suffered once the series switched to 800cc bikes, especially as Honda switched their development focus to corner speed, and the European 250cc style.
Stoner used his dirt track skills to control the fearsome Ducati Desmosedici, the bike which destroyed the careers of so many other riders. Stoner’s switch to Honda coincided with Shuhei Nakamoto’s changed approach at HRC, putting more emphasis on rider input, putting more control of the rear tire back in the hands of the rider.