LeMans and Dakar both had to swing the rules massively in favour of the diesel to make them competitive, otherwise VW/Audi were going to pull out as their money making arm is economic diesels for road cars. Money speaking at it's finest.
Give them fair rules and they wouldn't see which way the petrols went - in fact, the few series still running open engine regulations between the two are the ones I named, and petrol wins, hell, even the trails guys crawling along at a few mph are switching to petrol as it means a lighter rig with lower CoG...
The reason most military vehicles are diesel is nothing to do with torque, it's fuel economy and the ability to run on a wide range of fuels from vegetable oil to kerosene - fuel supply isn't always perfect in a war....
Fenris has a point - for his model of car - if the car had the same size petrol turbo model available, you'd find it also had much more torque.
The problem is it would also have much more power and would probably end up with higher gearing, hence the clutch slip problem at crawling speeds, but that's a gearbox issue rather than an engine one