* Bulgarian support for the EU is pretty low and people didn't think it made their life much better
* Bulgarian support for Russia is very high, like 50%, probably due to their historic help in kicking out the Turks
Also, under under the Communist rule supported by USSR, they indoctrinated people into a version of history that Turks are the absolute evil, and Russians are the absolute angels saving them from the ottomans.
I.e. in pre-EU era it was called Ottoman slavery, later they start calling it Ottoman era as it was more accurate as Ottoman’s system was based on collecting taxes and resources from the conquered places when giving them plenty of autonomy. Obviously not ideal but far from slavery.
Devshirme, Janissary corps, Batak massacre? There is huge blood debt that is owed to the Balkans and Armenia by the Ottoman Empire and their successor states.