Dive Deep into Creativity: Discover, Share, Inspire
With the responsibility of leadership and the dangers of pedestals and hero worship being such major themes, it only makes sense that all three of the film's leaders would show their true characters, and in doing so seal their fates, in moments where they have to kneel/bow.
Sentinel Prime essentially sets the entire second half of the film in motion when both the heroes and we as the viewer see him kneel to the Quintessons. It confirms everything that Alpha Trion was just telling them/us about him, and it's also the very thing that ends up getting broadcast to Iacon in order to finally expose Sentinel and turn the public against their False Prime.
For all his superficial charisma and his talk of looking out for the little guys, Sentinel himself is truly nothing more than a self-centred, spineless coward, who couldn't care less for the needs of the many and gladly bends to the will of bigger bullies/oppressors in order to keep himself in power.
After learning of Sentinel's betrayal and being subsequently captured with the High Guard, D-16 makes a point to stand while in custody and adamantly refuses to kneel. Even when Sentinel begins beating and torturing him, D-16 makes it abundantly clear that he has no intention of bowing to him or anyone else ever again.
In better circumstances this could be a heroic trait, a courageous defiance and the willingness to stand up in the face of injustice. But it just as becomes a negative one, and it's one of the last warning signs to the kind of leader that Megatron is going to be.
He may have started out with good and heroic intentions, but because of this Megatron sees himself as superior, and whether by choice or by force, he expects his fellow Cybetronians to rally behind him just as they did with Sentinel. While he sees himself as a revolutionary, in the end he's just going to become another tyrant.
And then we have Orion Pax. For much of the film, he's a far cry from the noble, legendary leader that we know and love from other iterations, but he starts to grow into it as he devises the rescue mission, and is tasked with rallying his fellow miners to help.
Having gotten a major upgrade since the last time he saw them, Orion now towers over his former peers and they're utterly awed by the sight of him. Rather than trying to take advantage of their admiration or even intimidate them with his new size and strength, Orion almost seems frustrated by the new height difference, and before beginning his speech he kneels down to literally speak to them on their level.
Orion doesn't make a point to do this, no one has to ask or prompt him to, in fact he himself doesn't even give that much thought to it, it's just his first instinct for how to best communicate. He may look larger and stronger now, but he still values the miners as his friends and his equals, and nothing is ever going to change that.
Gaining the Matrix later on may have gotten him the name, but it's this moment when Orion truly begins to embody the true core and heart of Optimus Prime. Powerful and inspiring, yet humble and caring. Or perhaps, as the legendary Peter Cullen himself has always said:
"Strong enough to be gentle."