Destroying a system means there isn't anything in place and also that you weaken the power of your own side because you had to go through all the violence needed.

That's obvious but it also explains why worse system can rise, but also that it's not always a doomed endeavor. I think the context has a lot to do with what will occurs next.

The best exemple i could give is the French Revolution. It was followed by the worst Napoleonic wars. But its philosophers founded the building block for the republic that's still in place to this day.

The red revolution against tsarist has brought a lot of positive foundation from which Russian could arguably have builded upon after the war, if not for Gorbachev.

I'm not gonna go to much into any hypothetical but what Lenin created had a real and positive influence in the rest of Europe at least.

At the worst end of the spectrum Iran really had nothing left to build upon, the situation there is catastrophic on all front. So if not for the US the country isn't gonna stand on its legs any time soon.

I think the evolution of the end of a system, even through those three exemple, can go into so many different path. It's hard to really predict anything, especially without taking into account all the parameters and context.