Because it’s never “extinguish” from the “extender’s” perspective. They extended it and scooped up all the customers, mission accomplished.

I think the first 2 e's actually did predate extinguish

They just used EE internally. "Extinguish" was added by the someone suing them and the media.

Because that looks really bad if the email is made public as a result of a court case, like this one was.