I don't think that anyone who does a protest e..g. a march, demo, sit-in, loudspeaker outside Downing Street seriously thinks that one action by itself will mean they automatically achieve all their aims. But taken as part of a concerted campaign, that's how change happens - look at anything you like from workers rights to political parties to votes for women to Brexit - none of these things happened because of one single action but instead because of thousands of people each contributing in their own way towards the same goal.