The eyewitness weren’t ‘disregarded’, many had already died. That’s why Israel’s Supreme court cited evidence spoilage (legal term not derogatory) as the main reason for overturning the one conviction.
Luckily, it seems the new evidence is documentary, plus now we know that he did go by the name on the ID when he applied for his US visa, so that defense is out the window and actually is another piece against him.
Heck, they might even have a competent charge to bring against him by 2015...
The problem is, the “mystery” witness will now have to testify in Germany to establish the “Marchenko” name being used, no one knows who that witness is, whether they are alive or not, or even if they would be willing to testify in a German proceeding.