It's a scene that raised our old-timey Transformers fan eyebrows a bit, because Optimus's maker is a character not yet seen in the live-action movies, but one who looms large in the mythology of the Transformers...almost as large as his twin brother, Unicron, long rumored to be an antagonist in The Last Knight.
As ComicBook.com's Kofi Outlaw previously explained:
Unicron is the evil twin brother of Primus, who is the creator god of the Transformers. While Primus is a force for benevolence and good in the multiverse, Unicron's only function is to bring chaos and destruction, with the goal of being the only god in a lifeless universe.
Unicron was created by The One, to explore the universe as it began. The One then divided Unicron in two, creating Primus as his twin. The war between Primus and Unicron has gone on since the beginning of the Universe, and could be the bigger story arc that Transformers: The Last Knight filmmakers have hinted at.
That's bolstered by the idea that much of the imagery in the film's trailers thus far has been at least somewhat evocative of Unicron, a character who in his first appearance in Transformers: The Movie rebuilt Megatron from near death and used the upgrades he installed in the villain to take control of him and bend the newly-minted Galvatron to Unicron's will.
There's a lot of buzz that such an event could explain why Optimus Prime seems...not quite himself...in the trailers.
To be clear, the "maker" of Optimus Prime is Primus, who in one of the major timelines (there are a lot of takes on Transformers, but the Aligned Timeline, from which this story is drawn, is kind of a greatest hits version of the universe) created 13 Primes to aid him in his millennia-long battle against his twin brother, Unicron (who, as these things tend to go, is a destroyer to offset his brother the creator).
(And, yes, both he and Unicron are planet-sized Transformers, which is not only objectively cool but could explain some of the imagery seen in the new trailer.)
Optimus ends up as the last of the Primes -- which could be the source of the whole "The Last Knight" thing.
Having Creators -- plural -- after Optimus in the previous movie (and seeing him head into space to take them on, then appear dead or near death in the first trailer for The Last Knight seems to suggest that if he found them, it didn't go well. but given that most versions of the Transformers mythology has only one "maker" or creator for Optimus at all, perhaps there was a misunderstanding inherent in the mythology of Age of Extinction.
The thirteen (the Primes or the Knights) were the original owners of the Autobot Matrix of Leadership, the artifact that Sam used to resurrect Optimus in Revenge of the Fallen (and which was the only thing that could destroy Unicron in Transformers: The Movie).
Could this turn out to be relevant information? It seems likely but certainly isn't guaranteed...but when you're sitting there going "Wait...who is Optimus Prime's maker, and how is that different from the 'Creators' from the last movie?" this is the best answer we've got.
More Transformers: The Last Knight: Mark Wahlberg Goes Exploring In New Transformers: The Last Knight Image / The Last Knight Official Poster released/ Animated Movie Takes Place In Live Action Continuity / 5 Facts To Know About Unicron / The Last Knight 5 Questions Raised / Internet Reacts To The Last Knight /The Last Knight Trailer Released / The Last Knight Trailer Stills Gallery / Paramount Thinking Of Transformer Films Without Key Character
Transformers: The Last Knight is set for release June 23, 2017.