Okay, let us debate your comparison of Nicholas abdicating and Bush being impeached. I promise no derision.
Impeachment is a an action of civil law, not criminal. Its sole purpose is to remove a sitting president from office because he has committed "high crimes and misdemeanors." Impeachment is simply the process of trying the president before the Senate. If the Senate votes that he is guilty, then he is removed. Impeachment doesn't necessarily mean conviction (Johnson and Clinton). If after he is removed from office his crime(s) are considered to have been criminal offenses then he could be brought before a grand jury and indicted, then tried, and if found guilty, sentenced to prison. If his crime was murder, then he might well be executed for it.
Now, in Nicholas' case. He abdicated, of his own free will, although some have tried to suggest he was forced to do it, but that is debatable as we have been doing. In any case, he was removed from office.
Ordinarily that would have meant he was fee to go and do what he wanted. However, many in Russia considered Nicholas to have been a criminal. This was why the Soviet insisted he, and his family be held under house arrest. And, many called for his trial. In fact, I am convinced that is what Yakovlev was trying to do--bring Nicholas, and his family, back to Moscow, where he would be tried in a show trial. He might have been convicted and sentenced to prison, or execution. His family would probably been sent into exile. So far all has been civil. When however, the Ural Soviet found out this intent they intervened to hold the family because they didn't think Nicholas would be judged. They wanted vengence, or revenge. Still, they kept the family in fairly civil conditions. His trial was debated by the Ural Soviet, and discussion with the Moscow Central Committee. What happened was the outbreak of the civil war, and close to Ekaterinburg. That meant the family could be rescued and taken away. The Ural Soviets were not going to let that happen. When it became clear events were moving too fast, they decided to kill the family. They could well have simply taken the family out into the city, and let the crowd take their vengence. That would have been truly horrible (as the September massacres in the French Revolution). Horrible as their execution was, it was fairly quick, if not instantaneous, in private, with no public humiliation of the women and then defilement of their bodies. All this occurred due to a special set of circumstances. Only those Romanovs who had been sent to the area controlled by the Ural Soviet were killed. Most of the others got away. The exceeption to that were the four grand dukes in Petrograd who were executed in 1919. And that happened because the civil war had truly become un-civil and terroristic, on both sides.
Let us consider a what if. What if the Whites had won and taken Lenin, Trotsky, Zinoviev, Sverdlovsk, et all prisoners. What would their fate have been, and how civil would it have been?