Demonstration bring people together. They talk and exchange ideas, minds change. Writers cover the events, sometimes they modify their ideas and often they change how we discuss issues. Politicians see this and decide what ideas aren’t represented and decisions are made accordingly. It’s basic stuff.
A well mannered protest like this could shift opinions. Perhaps some of the public expected climate change protesters to be like continental May Day protesters (dressed in black, there to smash things, happy to use violence). The fact they aren’t... means the ideas might reach a new audience.
Even ‘failed’ protests such as the Jr Doctors strike in 2015 changed some things. Who didn’t modify their opinion of J.Hunt, who thinks he could ever now fight an election?