This. The Brits have a first past the post system. Greens now are winning mayorships and parliament seats and making deals with labor not to split the vote in their favor because they have been building local support for decades.
They are a force in their districts, so they get elected to office in their districts. Do that to a few dozen districts and you can meaningfully affect the balance of power in Westminster. Then you start getting into coalitions and supplying ministers.
You can’t just wake up once every four years and hope to be anything but a spoiler candidate.
That’s the whole point of the bulwark. It’s the official organ of never-trump republicans.