The buffer didn't save Leningrad, Finland didn't even attack leningrad or plan to, they stopped at the mark of their territory.

Yes it did and almost made the city fall. Its also where we crushed and Maneiherm and his troops.

And I quote ( see what I put in bold)

Although the Finnish troops on the Karelian Isthmus didn't actively participate in the Siege of Leningrad, merely just their existence contributed to the siege by hampering the supply of the city around and across the Lake Ladoga

The defeat was a humiliation to the Soviet Union because they had to execute their own troops for a cause to the war and lost hundreds of thousands of more men.

Please not a single Russians take that seriously or military historians.

For example , one of the biggest military humiliation in the history of the USSR was also at the end of the Germans in the first phase of their invasions when they encircled our army in Ukraine. But not a single person would say that we lost the war or that we still feel humiliated .

What matter is who got what at the end.

The Anthem proves that the Soviets Planned on the invasion as quoted:

Its a folklore song that was written by a general not even the state it proved norhing at all.

The Party Secretary was a big deal on Russia,

This is the party secretary of Leningrad

This is nothing at all. Decisions were took in Moscow in the politburo

The Soviet demands were an honest causi beli as it overlapped entirely over the Mannerheim line

We got it anyway , did we invaded Finland after ? The answer is simply no. Wich show that Fins were affraid for nothing.

The "folklore" song was made by a soviet general who was leading the invasion into finland.

A folklore song is not a proof at all

Molotov planned on invading Finland, Are you that stupid to think that the "Finnish Democratic Republic" would be legitmate?

They didnt care if it would be legitimate or not they wanted a quick way to get the territories they asked.

See your own link