[gruez]

and why would the external marketing agency have a full copy of the movie, with no DRM?

[Rjevski]

Maybe whoever sending the content to the marketing company did the mistake, and the marketing company just obeyed their orders and uploaded it without further checking.

[dewey]

Maybe they also cut and edit the trailer? I don't know how they work internally.

[gruez]

quick search says that trailers are either made by specialized companies, or by in-house departments.

[dewey]

I guess that's true in 100% the cases then and there's no room for a human mistake left in this case ;)