The Greens were between a rock and a hard place.  Back the BC Liberals which would make making it to four years easier, but guarantee a massive backlash and wipeout of the party next election or back the NDP which has a shaky command and hope they can get PR passed.  If PR fails it will hurt them next time since if the NDP does a good job, people will vote for the real deal thus the NDP will get all the credit not the Greens and if they do a bad job, people will blame them for enabling it so they really need PR to pass if they want to improve next time around.