They and their actions might be too extreme for many, with very public displays in art galleries garnering much media attention coupled with bring coal shipments to a stand still by suspending themselves from coal loaders etc.
But they have grabbed attention and started a broader discussion about how far is too far when it comes to limiting fossil fuel use, etc.
There is already widespread awareness that something needs to change and these tantrums are just noise drowning out any useful signal.
I've seen no reports of any serious attenpt to vandalise a painting, get a grip.
In every case it's been attention grabbing performance "art" involving a famous glass covered painting.
An actual attempt to actually vandalise would look very different.