The use of petrol engines versus diesel engines during the second world war was a matter of expediency. Because both sides needed a very large increase in equipment production, they used whatever they already had, and increased production as much and as fast as possible. If you have a reliable petrol engine, available in numbers, you are going to use it, even if it would be marginally safer to use a diesel engine, which you need to develop and build a production line for. There was also the logistics of fuel supply. Petrol was refined in quantity. To start a separate diesel refining line, and the separate logistic train to get it to the users, would have taken to much resource from the immediate issue at hand, I.e. in the first years of the war, keeping a deterrent against the German navy operational, to deny the German navy control of the English channel and the North Sea, simply to keep Britain in the fight.
Once hostilities ceased, and development continued after the war, tanks and ships soon became diesel fueled, although not simply because of safety reasons.
If you compare statistics for boat fires, you’ll find that petrol engined pleasure boats regularly catch fire, or even explode (usually when the engine is started without purging the engine bay), and the number of times Diesel engned boats do the same, can be counted on one hand.
LPG is dangerous. Anybody arguing the use of LPG or Propane or Butane over diesel, as a propulsion fuel, shows a total lack of understanding of the subject, and can be ignored.