I think specifically of Imperial Russia and the Byzantine Empire because they had some broad similarities, both being total autocracies heavily backed by Orthodox Christian beliefs and that tended to deify the portrayal of the Emperor. However Byzantium was infamous for the scheming back-stabbing nature of the throne that saw no small number of Emperors assassinated, with new dynasties rising and falling.
Meanwhile the Romanov dynasty lasted over 400 years, with the showdown between Peter I and the regent Sophia being the only case of something like a coup, or Catherine II's takeover from Peter III. Nothing like the seething mass of conspiracy and plotting that dominated the Byzantine courts. So what made empires like Byzantium so much more prone to this sort of political instability than others like Russia?
For a look into why the political system wasn't as stable, you can look at my post here: https://www.reddit.com/r/AskHistorians/comments/40nmay/what_prevented_the_romanbyzantine_and_ottoman/
Although I wanted to add one thing here by saying that the reputation Byzantium has as a wash of civil wars and assassinations and Emperor killings is, in my view, quite overblown. The Byzantine Empire was actually, when viewed as a whole, quite stable at the top and for vast periods of time it was the central court and bureaucracy that had sole power over who was allowed to be Emperor. From the rise of Theodosius I in the late 5th century to the overthrow of Maurice in the earth 7th century, for example, there are over 200 years of rule that saw peaceful exchanges of power, during which two different dynasties rose and fell. Likewise, from the mid 9th to the late 11th century, the Macedonian dynasty saw continuous rule outside of the rule of Romanos I Lekapenos, although his usurpation was peaceful for the most part.
The only times there are really an uptick in political killings are when you would expect there to be more people getting killed, namely: minority emperors, weak emperors, and military-political disaster.