Why did the Hivers assassinate Emperor Strephon? Why did the Hivers allow the Third Imperium to fall? What are the Hivers' plans for the future of humanity?

There are those who say that nothing takes place in charted space without the Hivers having anticipated it, planned it, shaped it, brought it into being by patient, careful manipulation.
The Hivers are the manipulators-emotionless, perfectly rational beings possessed of infinite patience and subtlety. If interstellar history is a clock, the Hivers are the ones who wind it; the passage of time itself does their bidding.
If a tree fell in a forest, and no one was there to hear it, would it make a sound? And how come if there are trees falling down, you never see any Hivers running around with axes?
What do you get when you cross a golden retriever with a box of razor blades? How is it that the most efficient, merciless killers in the universe don't have a mean bone in their bodies? If violence is natural, guileless, and innocent, does that mean one need not take it so personally?
The lthklur are the most feared warriors known to man. To an Ithklur,
Vargr plunder is like a walk in the park; Aslan warrior spirit is the babbling of a toothless child. Other races make such a fuss over
violence-why not just do it and enjoy yourself?
To the Hivers, the lthklur are their trained, elite shock troops, lovingly perfected by millenia of manipulation and social engineering. No finer tool has ever been fashioned.
But as far as the Ithklur are concerned, they have the Hivers just where they want them. Who wants to be a boring taxi driver anyway? If the Hivers want to pretend they're in charge, what does it really hurt, so long they leave the Ithklur alone?
Who is manipulating whom? Is the Vargr wagging his tail, or is the tail wagging the Vargr? What is the sound made when an irresistable force collides with an immovable object?

Hivers and Ithklur
Because in space, no one can hear you scheme