The bolsheviks never targeted the cultural Cossack people, nomadic Steppe horse riders, but instead "Cossacks," Tsarist troops that ran down peasants on horseback. They had the same name because the Tsar relied heavily on recruiting the Cossack people, but it wasn't a random decision to commit genocide like you're framing. That's why your own link says information on the subject is highly blurred and contested:

Several scholars have categorised this as a form of genocide,[6][7][8][9][10] whilst other historians have highly disputed this classification due to the contentious figures involved, which range from "a few thousand to incredible claims of hundreds of thousands".[11][12][13]

Lenin didn't order the deaths of random people. Lenin led a revolution, one which overturned the incredibly brutal Tsarist system. Lenin did not unilaterally impose socialism, it was something fought for by the working classes. The White Army (the Tsarist forces), the fourteen capitalist nations that invaded Russia during its revolution, and the former ruling classes were all fought by the revolutionary peoples led by Lenin. In eliminating Tsarism, and establishing socialism, the transition from pure squalor resulted in doubling of life expectancy, tripling of literacy rates to 99.9%, free and high quality healthcare and education for all, the right to a job, certified home ownership, and much more.

Mark Twain spoke this of the French Revolution:

THERE were two “Reigns of Terror,” if we would but remember it and consider it; the one wrought murder in hot passion, the other in heartless cold blood; the one lasted mere months, the other had lasted a thousand years; the one inflicted death upon ten thousand persons, the other upon a hundred millions; but our shudders are all for the “horrors” of the minor Terror, the momentary Terror, so to speak; whereas, what is the horror of swift death by the axe, compared with lifelong death from hunger, cold, insult, cruelty, and heart-break? What is swift death by lightning compared with death by slow fire at the stake? A city cemetery could contain the coffins filled by that brief Terror which we have all been so diligently taught to shiver at and mourn over; but all France could hardly contain the coffins filled by that older and real Terror—that unspeakably bitter and awful Terror which none of us has been taught to see in its vastness or pity as it deserves.

The Russian Revolution was much the same. Hundreds of millions of lives were uplifted and saved by it. That is why Lenin is remembered as a hero even in post-socialist Russia.