That's not such a ridiculously simple motive though, I would argue, 1ord3vil. I raise this point because one of the things I've always enjoyed about the character of Colonel Vogel in Last Crusade is that I think he's a well-drawn portrait of a good soldier who's taken all his promotions with pleasure and honor but who really looks forward the parts of soldiering where he gets to get his hands dirty, as in the tank sequence as elsewhere. He's much, much different than Col. Dietrich in Raiders for this reason, and makes his double-duty as the military functionary and major enemy who enjoys beating the pulp out of Indy along the lines of the German mechanic and the head Thuggee guard work extremely well.
Then consider the closest analogue to the mechanic within Raiders itself, the tough sergeant during the truck chase. He's a hardened soldier, a slightly older man, who does what he does with grim determination but no particular joy, even when punching Indy in the arm. There may be the slightest of smiles as he's speeding up to crush Indy under the truck, but only the slightest, by my lights. He has nothing to show off, he has no real streak of sadism, if he's angry about anything it's about the loss of his men, but really, he's just trying to do his job.
There's nothing like that in the mechanic. The very first expression on his face when he emerges from his hut is a smile. He walks over, he swings his arms jauntily, he laughs, he taunts...one would imagine he doesn't have that much excitement in his life. He's a mechanic, he presumably keeps in shape, and that's probably about it. I don't see him being much for dissipation of either the sexual or alcoholic variety, although this speculation is quite unsubstantiated, of course. He likes the diversion. Right before he's sliced by the blade, Indy's on the ground - the easiest thing in the world would be to kick him, but instead it's "come on, get up" or something along those lines. He's not even that brutal; it's vaguely sportsmanlike. He's in it for the fun.