But now you're just employing another machine, which is not just made out of MOVs. The video describes in detail what actually happens. I encourage watching it

But now you're just employing another machine, which is not just made out of MOVs. The video describes in detail what actually happens. I encourage watching it, it's pretty genius, but the very short version is that you turn execution "off" for any code that is not in the "current" branch by switching over all MOVs to target a scratch space instead of their real targets, which means they still execute, but don't have an actual effect. Before each possible branch target, you check whether to turn execution "on", if it's the current one, i.e. making the instructions which are part of that branch affect "actual" memory again.