That’s the fault of our FPTP electoral system as much as anything else. In 1989 the Greens got 15% of votes to the European Parliament for example but won no seats. In 1999 proportional representation in the European Elections meant it was easier for small parties to win - ( which is why Nigel...
I know Caroline Lucas MP a little ( from my campaign days in the Green Party and later as a candidate myself) - I have always had a great deal of respect for her - one of the few conviction politicians I met in my political years in Brighton - her and David Lepper MP