Why did so many polytheistic people were converted into monotheism but the opposite way is so rare?

[TheReckoning]

     Monotheism in general leads to more powerful theologies which, when dominant amongst the general population, are better are propelling a country to be more powerful, relative to one’s a polytheistic religion being dominant. One reason behind this is that monotheistic religions tend to be a bit more “personal” than polytheistic ones, which makes sense- polytheistic religions tend to be more about the gods interact with one another, while monotheistic ones of course focus on how God interacts with human beings. Monotheist Religion therefore gives human beings more purpose, and more reason to be developed.

      Of course, more powerful countries spread their religion more than less powerful ones.