I was born in Sydney BC, I lived on Vancouver Island for 24 years... I just turned 30...
I'd say a lot of the liberalism started with the draft dodgers, followed by the "Socialized" immigration. I call this the "Soft Cold War", where old guards planted the seeds of socialism in the the young guard then set them free to leave, that way they "kill with kindness" and sow the seeds of socialism.
Canada has continually been sown with those seeds...
Yes, I'm sure that's part of it too. But you should see Vancouver now. It's more and more difficult to find white faces, I kid you not.
I'm not against all the immigrants, lots of the Asians are very hardworking and constructive. Many obtain University educations and become professionals. But they always bring, Mom, Dad, Gramma, Grampa, Auntie, Uncle......., those are the ones that are so easily swayed by promises of multiculturalism, special rights for "your culture", on and on it goes. Pretty soon, WE are the minority.
PS - Vancouver Island is a really beautiful place, Victoria in particular. But it has become quite Liberal also. University city I guess.