i see it like this (and granted not doing any calculations or nothing)
occasionally i've had the jeep stuck to the point where the engine just quit because the tourqe required to turn the wheels just wasn't there. this is the point where most people with more than a stock 258 break stuff, or, with a good driveline, get out of the situation. with gearing, the tourqe is multiplied, so the explosion in the cylinder can move the crank around easier. when lugging the engine, bigger boom in the cylinder wont make the tourqe the situation is calling for. hence the added pressure on the bearings.