What was the Molotov-Ribbentrop Pact and the Soviet campaign in Poland about?

u/incrediblyderivative - originally from r/GenZhou
Source: dude just trust me and my Nazi-sympathising grandpa.

u/TurdFerguson1000 - originally from r/GenZhou
This isn't a good take. If the USSR had any interest in recreating the borders of the Russian Empire, then why didn't they annex Finland after their victories over them in the Winter War and Continuation War? Why weren't the old territories of Congress Poland annexed, when they could have easily chosen to do so at the end of the Great Patriotic War? The land that they occupied (mind you, only about three weeks after the initial German forays into Poland on September 1st, 1939) wasn't even Polish to begin with, but filled with ethnic Belarussians and Ukrainians that had previously been part of those respective socialist republics but then had their land taken by Poland and its reactionary military government at the conclusion of its war with the Soviets in the 1920s. The land taken from Romania was A. Taken from a reactionary monarchist state allied with the Germans, and B. Not secured to recreate the Russian imperial borders but rather because it was traditionally Ukrainian and Moldavian territory that they sought to reintegrate with their respective socialist republics (this is also true of the easternmost Czechoslovakian territory taken at the end of the war with Germany, which wasn't filled with many Czechs or Slovaks but in which many Ukrainian people had resided for centuries prior). Territory taken from Finland was largely intended to simply bolster the defensive capacity of Leningrad from a prospective attack or siege (which ultimately did come to pass from 1941-1944), and while I'm not very well-read on the history of the Baltic States within this period of time, people I've talked to on the Baltic SSRs sub have showcased evidence which suggests that many Lithuanians, Latvians and Estonians willingly petitioned to join the USSR out of a mixture of fears of being occupied by the Germans (who were hell bent on exterminating many of them, and ultimately did during their occupation of Eastern territories from 1941-1945) and out of loathing for their existing governments at the time, which similar to Poland, were largely reactionary, military-dominated governments that had done little to alleviate economic hardships caused in part by the Great Depression. And regardless of all that, the simple fact remains that the Soviets weren't the genocidal maniacs agitating for things like Generalplan Ost, and used their non-aggression pact with Germany as a means of helping people like Jews and Romani to escape from territory that otherwise would have been taken over by the Nazis, and in which they would have been enslaved or killed.

The truth about the Molotov-Ribbentrop Pact is that it was merely a non-aggression pact between the USSR and Germany, which the former sought in order to give itself time to better prepare for a war with Germany, while the Germans were busy fighting the British and the French elsewhere (if such a thing is to be considered an "alliance," then that would have made numerous countries like Britain, France, Poland, Latvia, etc. all allies of Germany as well, as each of them possessed non-aggression pacts with Germany throughout the 1930s as well). During the Sudeten Crisis and in the lead up to the German invasion of Poland, the Soviets had sought to create anti-fascist alliances with these states, Britain, and France, and had offered to station soldiers in Poland and Czechoslovakia to deter German occupations of those countries, but every such offer was rejected, leaving the Soviets with little choice but to seek a temporary peace with the Germans to bolster their own military capabilities in the meantime.