I must admit

my opinion about him changed after reading Samantha's testimony and 2003 interview, Polanski's actions are condemnable and come at least very close to rape.

Despite this I think the case should be closed, it happened decades ago in very different times (see very low original sentence) and he also paid Samantha money and cannot return to his homeland.

A renewed trial would benefit neither Polanski, Samantha or society.
Samantha's requests to drop charges is IMO the most important reason, she made it very clear she suffered more from the results of the molestation than from the molestation itself.