GMAT Critical Reasoning (CR) | Re: Until now, this painting was believed to be a self portrait

sincerely, I do not get how C is right...
the conclusion states that the painting might not be a self portrait.
then we have 2 premises...
1 - golden chain
2 - sword on hip
then we have a fact K>A.

how does C strengthens the conclusion that is is probably not a self portrait?
what if the artist wore the chains so that he would get himself a nice self portrait?
how does this mean that it's not a self portrait???? I dont see why we can not infer gentleman is not the same as artist, or that gentleman