It has to be him (judging by the amount of BTC in there, I'm pretty sure this is the case), otherwise that means his wallet is compromised.
I really wonder:
1. Who is Darkstar? How did the collaboration between him and Chipmixer happen? Why did Chipmixer chose him instead of other famous signature campaign managers? As I see, he has rarely managed sig campaigns.
2. Why did he disappear after the Chipmixer incident? Is he afraid that he may get caught?
By the way, what happened to Chipmixer owner, is he arrested or is he in the list of most wanted people?
To answer your question: Number 1, we don't know him personally, but DarkStar has been here since 2015; he's quite popular and trusted here on Bitcointalk, just so you know. As far as I know, he rarely manages signature campaigns because he focuses on managing the Chipmixer signature campaign. Number 2, he didn't disappear; he's just taking some rest, as he stated in his bio. He might want to not get involved in what's happened with Chipmixer.
Regarding Chipmixer's owner and the situation happened to Chipmixer case, this article might help to answer you question:
Germany and U.S. Seize Over $46M Crypto Tied to ChipMixer Investigation