The article feels like AI hallucinated slop. Just a quick scroll through the page:

* Sviatoslav was not a local ruler - he ruled Kievan Rus' 1500km north-east and he remained a pagan until his death, even if his mother had converted to Christianity.

* Sviatoslav was born nearly 60 years after both Cyril and Methodius had died.

* In 890 Boris was no longer in power but his firs son, who coincidentally tried to reverse the Christianity conversion and was kicked off the throne a few years later.

* " Just after the invasion of Ukraine in July 2021" check the date.