Could it be their business model changed after the mixer ban on Bitcointalk? I can imagine they lost customers and advertising, which may have changed their long-term perspective into realizing an exit scam is more profitable.
Or:
I've seen many scamming mixers over the years. Until recently, I didn't realize some mixers may just be created by non-scamming bad guys in need of good people looking for privacy. I can't be certain which mixers fall in which category, but by now I think it's likely both exist.
Could it be they were actually "the bad guys" who didn't need more "good guys" to exchange their money, so they decided to keep everything now?