This graph shows support for gay marriage in Estonia by age group and language (blue – Russian; red – Estonian).
The older people lived in one homophobic country.
Amongst younger people, Estonians tuned into Estonian language media, which I imagine is highly Europeanized, or even went straight to the source (English language media). Russians tuned into Russian media, which turned in an anti-LGBT direction in the late 2000s.
People are products of their media environment.
A similar process played out after WW2 in Europe with social and cultural trends in the west becoming synced with American developments while the Iron Curtain acted as a kind of ideological “deep freezer.” This variable development between Estonians and Russians within Estonia is that but in miniature.