Nice summary.
I believe it was Peter the Great who left a message for each Russian Tsar after him. The note said "Take Constantinople". Paraphrasing here.
I think its very interesting that Russia claimed it's third Rome. Slavic people generally were focused on the Byzantines.
Serbia is a good example of this. They adopted their coat of arms from the Byzantines as well.
Bulgaria has a long history of trying to become Byzantine as well. Bulgarians were promised the Byzantine crown, but were betrayed. Their Tsar went mad after this.
en.m.wikipedia.org
I think Russia did a good job at capitalizing on their opportunities. Russia wasn't seen as a friend to Europe, so Peter toured European states, learning of their culture and traditions, he managed to get the Habsburg Austrians on board in his war against the Ottomans, which legitimized Russia as a European power. Seeing Austrians ally with them.
Russia liberating the Balkans from the Ottomans was another smart move that endeared them to the Balkan Slavic populace, making Russia a defender of the Slavic orthodox people. The Ottomans had to officially recognize them as this. It was the western Europeans, who grew weary of Russia and started plotting against them.
I find it fascinating how the Ottomans fell like the Byzantines did. The ottomans tried their hardest to be Byzantine successors and in the end, failed like them.
The once great Ottoman Empire which was pretty progressive for its time, had turned into a backwater rumpstate. They were rapidly losing lands, they barely had any funds and were attacked from all sides. The once mighty Jannisarries were now the new Praetorian guards, who held the Empire hostage and decided who may sit on the throne. The Ottoman reforms caused more chaos than peace and in the end the Ottomans lost everything and were expelled from Anatolia. (The Osmanoglu dynasty was exiled, but in the 70s that exile was lifted)
The Ottomans in their final stages committed atrocities against entire population who were regarded as honorable and loyal by the state. Armenians.
That backfired massively because nowadays the former armenian regions are full of Kurds who commit terrorism. (The issue is more nuanced but has more to do with Atatürk than the ottomans)
An interesting note is, much like the Byzantines, the Ottomans tried to westernize, which pissed off the populations. Old ottomans used to wear big white round hats such as these and baggy clothing
View: https://imgur.com/a/ni0qFJu
In their westernization process they copied the German uniforms (German officers came and trained the Ottoman troops, which pissed off the population again, since Islam looks down on Christians as "gavurs", but now these gavurs are invited to teach us) and used Byzantine Headwear to replace the big hats.
Ottomans used "The Fez" as its commonly referred to.
View: https://imgur.com/a/ChKiJXz
The similarities between the Ottomans and the Byzantines is quiet karmic. They rose upon the ashes of the Byzantines, and fell like them.