You left me no choice, brother

It's comically absurd how Optimus says this to a "dying" Megatron.

Megatron was clearly winning the fight and looked like he could've / would've killed Optimus without the outside intervention (the Marines, the air support and Sam). Optimus realizes this towards the end and tells Sam to push the cube into his chest.

But Sam disregards Optimus and pushes the cube into Megatron's chest, "killing" him. So why does Optimus then say that line, like he was the one who killed Megatron or made Sam deliver the final blow?

Just a small nitpick, but maybe someone can explain it. This movie is near perfect and underrated af. Can't understand all the hate it gets. I was never into the Transformers cartoons, so I guess I don't have a problem with Michael Bay's take on it. RoTF was a near perfect sequel to it too, IMO.