The movie is vague on this part. Was it Hamilton and Brown from the Circus, who traded off Solomon, whilst he is unconscious, or was it someone else?
I know that before the end credits it said that he sued them IRL, but it also says that they were acquitted.
Is this something that has been investigated upon, and if so, was it them?
I would imagine the only reason they were acquitted is because it was a black guy suing them - however I'm not from the US and only learned through this film that there were free black people at a time of slavery. They really should teach more in schools (we learned nothing of America at all in history class)
shareAround 10 years after Solomon's release, one of our most famous cases went before the US Supreme Court. The "Dred Scott" case. What makes it one of our most famous cases is a line uttered by Chief Justice Roger Taney at the conclusion of the case. That blacks "had no rights which the white man was bound to respect; and that the negro might justly and lawfully be reduced to slavery for his benefit. He was bought and sold and treated as an ordinary article of merchandise and traffic, whenever profit could be made by it."
So your guess is almost certainly correct.
And...it is a mindset that the US is still virtually destroying itself trying to reconcile, over 150 years later.
No man lies so boldly as the man who is indignant.