Indeed it was, Russia was afraid that Germany would attack the USSR through Finland. Ironically the Winter War caused this to happen in 1941. The Finnish-Soviet relationship was also not exactly great after the 1918-1923 period, although it had been slowly improving, the trust was not there.
Today, this is not so much of a concern, Germany isn't really talking so much about conquests in the east these days.
Also WW2 had already started, this was part of the same deal between Germany and the USSR that partitioned Poland for the Nth time and allowed the USSR to occupy the Baltics and grab Bessarabia (today Moldova) from Romania.
Finland didn't quite lose a quarter of the terrory, there is a
map here. But almost 15% of the Finnish population (500.000) was evacuated and had to be resettled elsewhere, something which would shift demographics especially in many previously majority Swedish speaking regions.
But again, like with Ukraine, imperial ambitions were present too; Finland had been part of the Russian empire and the USSR had supported the reds in the Finnish civil war in 1918 and lost. A quick 3-week special military operation was put together to march into Helsinki with the oppressed Finnish workers throwing flowers at the marching Red Army. They even brought the marching bands with them as part of the initial offensive. Ukranian mobilized troops were shipped up to Finland with no proper winter equipment and aparently were not sure where they were or why they were supposed to fight a war.
There are several similarities between the current war in Ukraine and the Winter War, but also many differences, most obviously that Finland ran out of ammunition and lost after 105 days. It was not the victory the USSR had hoped for, but it was a victory for them nevertheless.