Campaigners explain why they’re convinced all it takes is support from a few powerful firms and people to change the fundamentals of Bitcoin.When environmentalist groups in March unveiled a campaign to move Bitcoin’s code away from the energy-intensive proof-of-work (PoW) model, many bitcoiners scoffed at the idea. Setting aside the question of whether proof-of-work mining is the environmental peril the activists claim it is, many cryptocurrency veterans doubt the strategy could work. That st...