That's like saying french and spanish are the same because they both descend from the roman empire.

Russian identity stems from mongol oppression, while ukrainian identity comes from being part of the Polish-Lithuanian Commonwealth. Their paths diverged around the XIV century.

Ukrainian nationalism was strong throughout the XIX century. And russians have always tried to squash it since then.

What is true is that Lenin was not a russian supremacist, and he genuinly believed in cosmopolitanism. Thus, he offered a space for ukrainians intending to buy them to the communist cause.

Let's remember that many ukrainians were extremely in favour of bolchevism at Lenin's times. Tatars were mostly anticommunist and western ukrainians were mostly nationalists. But in eastern and central Ukraine were mostly communists and anarchists.... until Stalin betrayed them and did the genocide.