I think that most coup d'etats weren't. Also surrendering or suing for peace does often cause major changes (v. Japan after WWII) and is rarely preceded by protests (which would typically be considered treason).
I expect that looking for edge cases in the meaning of "preceded" (I expect manifestations in support to sometimes start after the event that caused the change to be inevitable) and "major" (e.g. a German court has recently ruled that being able to cause oneself to die is a constitutionally-guaranteed right -- is that major?) might yield more examples.
legal aspects of suicide
> The German court example intrigues me – I would definitely consider it major and I wonder how it happened. Do you know more about the story?
See https://www.bundesverfassungsgericht.de/SharedDocs/Entscheidungen/EN/2020/02/rs20200226_2bvr234715en.html;jsessionid=180FE6377D3107753F22B95A5BB4752D.2_cid377 for a reference to the actual decision. That also implies that it's a result of complaints about unconstitutionality raised by people wishing to die, organisations that wish to enable that, doctors that wish to enable that, and lawyers that wish to enable that (all of them alleging that the criminalization violates some sort of constitutionally-guaranteed right they have).
Btw. I'm guessing that complainant III.1 is Dignitas.
> rarely controllable towards a specific change (technological progress).
What about invention of hormonal birth control?
@robryk Huh, yeah, that probably counts. Nice one.
The other attempt at technologically pushing for sociopolitical change is arguably Bitcoin, but it's still unclear whether and how much that will be successful.
@robryk Very good examples in both responses, although kind of useless for the purposes I was hoping for – my own fault for asking the question too broadly. :P
I've been thinking of alternative ways of influencing sociopolitical changes within democratic countries. Most of the ones you brought up are either not acceptable in these situations (coup d'etats, war, terrorism) or rarely controllable towards a specific change (technological progress).
Examples I got from other sources include being an authoritarian regime (China's move towards ~capitalism in the 80s) or being influenced by politics of other countries (most of drug politics in Europe following US internal struggles through their pressure? not the strongest example). The former is again not acceptable, the latter maybe technically could be, but you would have to somehow influence the politics of the first country, so you go back to the original problem.
The German court example intrigues me – I would definitely consider it major and I wonder how it happened. Do you know more about the story?