They are vegan, they get involved at their school on environmental improvements, they make sure they don't waste etc. and they make sure to highlight the plight of the future to others.
I honestly don't know how you can look at Greta Thunberg and underestimate the impact she's had on public discourse on climate change.
In before trolls have a go at them for being vegan, this very respected recent meta analysis published in science clearly finds that going vegan is the number one thing you can do to help most climate change factors https://josephpoore.com/Science%20360%206392%20987%20-%20Accepted%20Manuscript.pdf
80% of soy is fed to animals for humans to exploit, so not really sure what you're getting at.
A plant based diet eliminates the vast majority of animal suffering (bonus points for reduced climate destruction, antibiotic degradation and future pandemic likelihood)