Also, why was everyone Ok with Russia taking all that land? Did they have to fight anyone for it, or did they just declare it all theirs?
Before the 16th century Russian conquest, there was the Khanate of Sibir. By the time of the 16th century the Khanate was very weak, and the Stroganovs hire Cossacks to conquer it. Yermak Timofeyevich led these Cossacks.
Indigenous groups were also massacred, especially in the 17th and 18th century
Great Turkic Khaganate (5 - 8th century) and the empire of Genghis Khan (13-14 centuries). In 1555 the Siberian Khanate included in the Russian Empire. Taybugina rulers appealed to Tsar Ivan the Terrible with a request for citizenship, and received consent.