I plead the fifth when I get pulled over, am I a criminal? I don't understand. It seems to me the absolute smartest course of action - place the burden of proof entirely on the opposition, give them nothing to work with you don't have to.
In other words, nobody is saying that he has incriminated himself by pleading the fifth. But in Uber's civil case, he has created some very bad implications and greatly worsened their position, and it wouldn't be unreasonable for them to see him as a liability at this point. This is not a mere accusation by Waymo — his actions indicate that there's something going on here.
And the fifth amendment protects you from "adverse inference" in criminal proceedings. It doesn't protect you in a civil suit, nor does it bind me or others in this thread or the general public to conclude that yes, Levandowsky's trucking company is probably heading for a wall.