On the UK suffrage:

Although non-historians often assumed the WSPU was primarily responsible for obtaining women's suffrage, historians are much more skeptical about its contribution. It is generally agreed that the WSPU revitalized the suffrage campaign initially, but that its escalation of militancy after 1912 impeded reform. Recent studies have shifted from claiming that the WSPU was responsible for women's suffrage to portraying it as an early form of radical feminism that sought to liberate women from a male-centered gender system.

Supported by the fact that those activities largely subsided as WWI took hold, and the conclusion of WWI seemed to be the first signs of suffrage, but not equal suffrage until ten years later, long after those activities had time to fade. You also cited self-harm activities, which also wouldn't be relevant to complaints about undirected vandalism, though they certainly engaged in that.

We see it all the time, an unsympathetic violent act incites resentment. Look at January 6th, is the general response "oh we need to give these people what they want" or is it "screw those guys". That was even as they targeted the seat of power directly relevant to the change that they wanted (to make Trump unelected dictator, of all things). For a protest to inspire change, it needs a critical mass of people to take their side. There has to be a story to tell that can garner support, and the fewer distractions and the less a protest alienates people on the fence, or reinforces the opposition, the better. This can be violent, but violence is a risk that may undermine your goals. It has to be loud and it has to be a lot of people and they have to convey a story that others can understand.