Jeff Bezos can't use signal because Amazon uses... a pricing algorithm? Call me a bootlicker but that's insane.
"Companies and individuals have a legal responsibility to preserve documents when involved in government investigations or litigation in order to promote efficient and effective enforcement that protects the American public."
But there is no responsibility to create new potentially incriminating evidence against themselves. Just because you are under investigation does not mean all your communication henceforth needs to be recorded.
And then Amazon (and Google) instructed employees to delete lots of communications, and to communicate outside normal channels, e.g., via Signal.
Similar to Elon musk, anything he might do or say could be very consequential to businesses he's related to