Brian Greenspan has an outstanding reputation (among judges and fellow lawyers, not simply with the public), and has no need to boost his profile or seek out clients.
While the cases where he defends fairly ordinary middle class people don't make the headlines, he does take on such cases, on a different fee schedule than that reserved for the Muzzo and Bieber cases. (One example where he did an exemplary job exposing police incompetence and tunnel vision was his defense of Steve Murray in Goderich, charged with (and acquitted of) the murder of his daughter Mistie).
As for winnable -- no, he doesn't take on exclusively "winnable" cases. You need look no farther than into the recent Muzzo case. That was absolutely unwinnable from the get-go. What Greenspan could do, and did, was damage control. He engineered the guilty plea and public expressions of remorse by his client (which could well have been absolutely genuine; I have no reason to suppose they weren't -- but they were also good PR).
These moves likely shortened the sentence his client received, but also laid the groundwork for a positive view by the parole board in the future.
I don't for a nanosecond believe that CN has seen the error of her sneering, supercilious ways - but her parents probably have realized the urgent need for damage control. They may not have appreciated earlier the extent of the evidence against her and the negative impact her testimony engendered. They are both medical professionals, and while they have a "modest" home they may (for all we know) have investments or savings they can access for Greenspan's firm to represent CN. I don't see the need to posit MB or DM providing the funding without evidence of same.
Someone mentioned her Pinterest account seemed to be down. I would hazard a confident guess that one of the very first orders from her new lawyer was some variant of Get that girl OFF all social media NOW! I was also surprised that she had not been coached by her previous lawyer in how to present herself in court -- a more self-effacing and regretful persona would have served her cause much better.
It's possible her lawyer did try to do this, with no luck. Parents may have laid down the law now; we aren't privy to such details. But I expect someone, not necessarily CN, has appreciated the seriousness of the situation and escalated their response.