Stalin was a non-figure for a long time.
In the late '80s and very early '90s he was a bad guy. They had an "unmasking" of his crimes.
This was embarrassing, and it "weakened" the country so it sort of faded. Then under Putin Stalin became a good guy. What he did bad vanished from the history books. What he did good is mentioned, but not in overly lush ways. He's sort of an understated savior.
In some areas--esp. among older, unreconstructed Soviet Russians--it's a crime to mention that he did anything bad. He was a good person who loved his country. What he did bad was either necessary and therefore justified, was appropriate to smash enemies of "the people" (again, that word "narod" that we hear oozing from the mouth of Ponomarev, Gubarev, Strelkov, and other "patriots" or lies told to defame the good-hearted Russian people and the brave, strong Russian soldier.
They have their pride vicariously rooted in Stalin and the glories of the USSR. To deny them is to strip them of their dignity and pride. To say they suffered for a lie is rather worse than telling a mother that her son died for a lost cause.