To gain access to Waymo’s design server, Mr. Levandowski searched for and installed specialized software onto his company-issued laptop. Once inside, he downloaded 9.7 GB of Waymo’s highly confidential files and trade secrets, including blueprints, design files and testing documentation. Then he connected an external drive to the laptop. Mr. Levandowski then wiped and reformatted the laptop in an attempt to erase forensic fingerprints.
A note on our lawsuit against Otto and Uber
Waymo Team

This is based on only what I read here:

But can someone explain to me why someone could connect any random USB drive to a computer here? Or why a DLP product either wasn’t being used or a policy wasn’t in place to track these types of documents?

There are so many different ways out there to protect and/or prevent USB devices from being connected. A security policy can be enforced via an Endpoint Protection product, Group Policy (on Windows devices) or other means for various other OS’s out there.

Also a good Data Loss Prevention product can have policies detect confidential data from being copied over. Both structured data and unstructured data.

Seems like a lot of tools either were not in use or not configured.

Just remember this is based only on the information in this post