The memory didn't have a lot of weight for me because it was so fuzzy; in fact, my first big Transformers "thing" was "The Return of Optimus Prime," which is of course sort of the happy fixfic epilogue to the movie's story.
But the scenes between Optimus and Megatron in the movie...
(Bonus screenshot: The most awesome frame of animation from the above sequence!
Bask in it.)
...and his subsequent death scene traumatized the hell out of a generation of kids, and probably cemented Transformers as a major franchise in the minds of a lot of people.
(Bonus screenshot: Dead Optimus Prime!
Stupid anecdote time: I once watched a stupid YouTube video where Optimus Prime sings a lengthy piece of opera before suddenly dying; the "turns his head as he dies" bit appeared in the sequence with a screeching clank sound. I think of that video every time I watch this scene.)
The brutality of the death scene in what had previously been a relatively light-hearted franchise (which was apparently inspired by Hasbro realizing "hey, our products are characters! We could kill them to explain why we're not selling them anymore!" in response to a GIJoe writer wanting to kill off Duke in the GIJoe movie-funny story, the death of Optimus Prime saved Duke's life because Hasbro got scared that killing Duke would trigger another outcry) was unintentional, but one could certainly imagine that they were trying to traumatize children without that context.
That's the only actual explanation I can come up with for the Death of Convoy advertisement.
(Bonus screenshot: Other dead Optimus Prime!
While the advertisement was made for the Japanese market, where brutal character death was much more common in animation, even animation ostensibly aimed at children, this scene is amazingly harsh. Seeing the mangled remains of a beloved character carted off by helicopters like so much
*The child actor who screams "Convoy!" during that commercial apparently showed up in the YouTube comments for the video, commenting that the ad's director "had me say 'Comvoy' instead. Never knew why." He also was enough of a fan of Transformers that he couldn't sit on his nondisclosure agreement and told a friend about Prime's death way too soon. His friend didn't believe him.
**Japan didn't get the movie until at least 1989, several years after Optimus dropped from Transformers fiction with only this*** as an explanation. (He did kind of show up again, but Japan casually killed him back off when the next season started.) They just kind of dove into the third season of the cartoon with no explanation at all. You think "Five Faces of Darkness" was confusing for the American audience...
***This and a momentary scene from the Headmasters cartoon, which wasn't a good explanation either. Shoulda doublechecked on the wiki sooner...