Voters in Canada have a long tradition of tradition of getting so sick of the incumbents that get flock to a previously marginal upstart. Sometimes the upstart flames out like the federal NDP. Sometimes the big political actors unite under the new label and the upstart becomes one of the two competitors for government like the BC liberals. The Green party was in the right place at the right time.
"Long tradition"? When have Canadians ever elected an upstart party like the Greens before?