There may be good reason to send him to prison, but the trial is all about Show. Since WW2, Germany has a complex in which they always need to show how "changed" they are from those days.
A lot of Eastern European and some other peoples collaborated with Hitler to merely survive or help themselves out- Slovakia, Hungary, Finland, Romania, Bulgaria, Croatia, Bosnia along with aid from some Irish, Spanish, Lithuanian and Ukrainian people. Sweden also traded a lot of iron ore to the Reich. IIRC, Demjanjuk was taken as a child laborer initially then moved up to guard. I'm thinking Mr. Demajanjuk's service was merely for protection. Going after people this late in the game is just senseless. I'm far from a Holocaust denier, but it's nearly as bad as me asking the British goverment or blacks asking Southern landowners for reparations. Nuremberg's out of the way and the worst of the criminals got what they deserved. It's over!