TL;DR: The "Bombshell" is Alphabet/Waymo's lawsuit against Lewandowski and Uber for stealing trade secrets, and an interpretation that Lewandowski formed Otto basically as a cover to get a big payday from Uber in exchange for the secrets.
The bombshell part specifically would be Levandowski arranging with Uber to steal Waymo tech, form Otto, and Uber would acquire Otto. In all of the reporting I read about this after the first filing, this was missed.
As someone who several years ago "managed" to take over a publicly traded company (via a federal judge's order once certain evidence was presented) and gather and present evidence of massive fraud, etc., and working entirely as an amateur in this effort, managed to aid in recovering assets and capturing the former CEO and sending him to prison for several years, I find stories of (allegedly) fraudulent action (and solid response) like this heartwarming.
If Uber had no self-driving car program to speak of before talking with Levandowski, and discovery shows they basically started from that conversation, then that would seem to open up all of Uber to any discovery process - they can't justifiably claim "it's the self driving car division that did all this". This seems much more than a civil process from my reading of it. It could be great theater.
If I was on Uber's BOD, I'd immediately relieve the CEO simply based on the allegations here, and if I didn't have the votes to do that, I'd immediately resign my seat.