Oleg has already started to see the weakness in Ivar and Hvitserk’s relationship, and he may use it to his advantage.
One theory is Oleg is determined to keep Ivar on his team, he will need to make sure Ivar’s opinions of him are not swayed in any way.
He may fear Hvitserk will convince Ivar to turn his back on him, and will therefore need to keep Hvitserk out of the way.
On the other hand, there is a chance Oleg has sensed Ivar’s plan to overthrow him, and so he will find a way to turn Hvitserk against his brother to make Ivar feel even more alone and powerless.
Hvitserk’s character has been building slowly across the previous seasons, and he is expected to play a huge role in the upcoming episodes.