In 988, Orthodox Christianity was chosen by Prince Vladimir as the state religion of Kievan Rus. This is how the vector of historical development not only of Russia, but also of the whole of Eastern Europe was forever determined.
In fact, the choice in favor of the Greek religion occurred long before the reign of Prince Vladimir. For many years Byzantium exerted a cultural and political influence on the Russian lands and demonstrated the strength of Orthodoxy.
In 955, Princess Olga was baptized. During the reign of Vladimir, the first Christian communities already existed and some Russian boyars were baptized.
Considering the fact that part of the population was already familiar with Orthodoxy, and also wishing to take advantage of friendship with Byzantium, the Kiev prince made the only, at that time, correct decision.
Nevertheless, next to Byzantium, there was another powerful state at the peak of its power — the Arab Caliphate. Historians suggest that if Vladimir was interested, then he could well have chosen Islam.
Several times Byzantium found itself on the verge of being captured by Muslims. In 674 and 717, the Arabs reached the capital of the empire of Constantinople and besieged it. At the same time, the Muslims invaded Spain and broke through to France and Italy.
With a successful siege of Constantinople, the Arabs would defeat Byzantium
Under the influence of Kievan Rus, Islam would have penetrated the northern principalities, the Baltic states and the Western Slavs. In turn, Orthodoxy without Russia as the successor of Byzantium would have gone into oblivion.
In the XIII century, the invasion of the Mongols would have met the united army of the Bulgars and the united Islamic principalities of Russia. Bulgaria alone
The Mongol yoke, which made the Russian principalities dependent on the Golden Horde and stopped their development for 200 years, would never have existed.
Most likely, Russia would have had a completely different look than it is now. After the fall of Byzantium, our country bore the title of defender of all Orthodox Christians and therefore sought to unite Eastern Europe under its own banner.
If Islam was adopted, Russia would be only one of the Muslim countries
Nevertheless, the development of Siberia would have taken place in any case: the main commodity traded in Russia was furs. And in distant lands it was in bulk.
Islam implies that slavery in any form is bad. They need to be freed and redeemed. But only if we are talking about Muslims. At the same time, the Gentiles were subjected to harsh persecution, massively turned into slavery and mercilessly taken out of the occupied lands to other countries.
Most likely, Russia really would not know serfdom. Instead of oppressing their subjects, there would be real slavery with the exploitation of «infidels», the same as in the Ottoman Empire, the Crimean Khanate and Africa. And no one knows which is worse.
One of the advantages of Muslims is polygamy and, as a result, a huge number of children. The rapid growth in the number of Russians would «plug in the belt» modern China.
The Muslim religion does not like innovation. The reforms of Peter I will never come to Russia. Science, poetry, literature and progress in general would develop much more slowly.
A distinctive feature of the upbringing of Muslims is obedience to fate. The proverb: «Everything that is not done, everything is for the best,» very characterizes these people. Russia would not know many of its achievements.
In addition, in Islam it is forbidden to borrow money at interest. It sounds beautiful, but in fact, in such conditions, an effective banking system cannot exist. You cannot open your own business without investment or take out a mortgage. By the way, today in Islamic countries almost all banks give loans at interest rates.
What would Russia be like in the end? Most likely, it would be less developed than it is now, moreover, it is strongly connected with the Arab world. The world would definitely hear about famous Russian scientists, doctors and other figures.