I want to know the answer to the following question:
Why did the attack by the Rus go so well on the coast at the start?
All the background I'm provided with is that "At last a Byzantine army arrived from the Balkans to drive the Rus' back, and a naval contingent reportedly destroyed much of the Rus' fleet on its return voyage (possibly an exaggeration since the Rus' soon mounted another attack).". Is that enough to answer the question?
Answer: no