Of a total of about 8 million Ukrainian refugees, why have some 2.8 million Ukrainians fled to Russia?

This is the largest refugee flight in Europe since World War II. The total population of the Ukraine before the war was about 44 million.

The reported high number of refugees to Russia is in doubt! Further, how many of these refugees were forced to leave the Ukraine for Russia and are thus not really refugees? Any such deportation of Ukrainians constitutes another war crime committed by Putin the Terrible!

Millions of displaced Ukrainians have not left the country.