Don't confuse the Kiev Rus with Russia. What is Russia today was originally the Grand Duchy of Moscow. The state was renamed Russia when Ivan the terrible was crown Tsar.
I think more context is needed.
The original Slavs were pushed east but waves of Asian invasion, Scandinavians (Rus) were invited to help fight especially on the eastern side. Eventually the Rus of Moscow became dominant and founded the first strong Russian state which eventually expelled the invaders and in the process became an expansionist empire.
Aside from this you have the Slavs being the original inhabitants of the general area with the original real civilization being founded on the western side by the Romans when they annexed the area, the flow of history (including the shift of the Byzantine mantel) is to blame for the gradual shift of the centre of Russian civilization eastward from the original Roman province.
What people miss is that there are multiple races as well as ethnicities inhabiting Russia not just one. For me an interesting bit is a lot of the satalite states originally were formed by mass peasent migrations away from corrupt Rus Noble influence.... which is where the fighting started once Russia decided to forcibly annex it's "lost sheep".
A lot of this can be explained as a more than millenium long racial conflict that never got resolved due to Russia being forced (either through circumstance or programmed habit) to fight all the time rather than develop. They were essentially THE buffer state for Europe against Asia... and ironically they never stopped fighting Europe as well.... lovely folks really.
EDIT: I happen to have read on the broad history recently BTW and am still digesting it.