I'm not sure why you are being downvoted, but this is at best only partially correct. Yiddish was supported along with pretty much all minority languages in the 1920s and early 1930s, but this support also ceased when the minority support policy was reversed (with token remnants such as the Yiddish being an official language in the Jewish "homeland" in the Far East). Following WWII and postwar persecutions of Jews Yiddish all but stopped being transferred from parents to children in the USSR. I remember how happy my grandfather (born 1928) was when it became possible to embrace one's Yiddish heritage again in the late 1980s); but he did not teach the language to his children.

The Russians (you mean Soviets) did nothing to preserve yiddish. They tried to exile the jews to a desolate remote corner on the fringes of siberia where they could practice their culture (not their religion) in a soviet communist framework.

I took Yiddish in university for a while. During the soviet years they tried to neutralize any hebraic or biblical references. For example, in hebrew the word for friend is "Chaver". It's the same in yiddish. But the soviets insisted that it be changed to the more germanic "fraynd". Similiarly, they insisted even on the changing of spellings to make the language altogether less hebraic and jewish - and more neutralized and soviet.