The problem is what they did didn't really have any meaning. They haven't really roused the public with their action, in fact their subsequent arrest has been more impactful for their cause than the actual action, and I can't imagine that was envisioned as a predicted outcome.

What they did was actually unhelpful because it allowed the government to label them as terrorists and therefore ignore them. Sticking to protests and writing to MPs and just making a general stink about things would, in the long run, have been more helpful because it would have never given them something that they could use as a stick to beat people with when they complained.