We think of Russia as the aggressor state toward the Baltics,but that is a relatively recent development. Historically it was Germany with no containing borders that was always in a state of fluidity regarding the territory surrounding her. We forget that for a long time,Germany was a threat to not only the Scandinavian/Baltic countries to her north and to Russia to her east,but her greatest historical rival was France.(another benefit with the formation of the EU - a final healing of one of the primary causes of conflict that disrupted the continent for centuries)
At some point in the 16th Century,the perception of dominant expansionist threat to the region switched from Germany to Russia. As a side note -you find countries in both the Middle East and the Far North who historically have spoken of both Russia and Great Britain as equal threats to their countries' sovereignty. In those scenarios,you go with a third power that is strong enough to offset the threat from the first two. And Germany was thought of as that third balancing power.
But it was that fear of an expansionist Russia that played an important role in how the perception of Germany changed in the region in the lead up to WW2.
The long term occupation of the northern region by Germany created an awakening of nationhood that had been largely absent before that time - previously most peoples identified by tribal associations rather than nation-state. The rise of nationalistic feeling and sense of ethnic superiority that enveloped Germany in the lead up to WW2, did not restrict itself to Germany.The events that move one nation usually affect all nations. What emerged at this time was this strange intersectionality where intense nationalism was on the rise,a longing by the aristocracy for a past glory came to the forefront and the fear of Russia's expansionist tendencies was also on the rise and that mix created a mentality in those countries that felt threatened by Russia,where the elite/aristocracy spoke positively of Germany as a protector of similar values,culture,and ethnicity against a Russia viewed as an alien people with a different set of values,culture and ethnicity. To the point where the theory of a Greater Germany was entertained in some surrounding countries and not with disfavour. (of course Germany did not reciprocate this fantasy of protective kinship,which countries realized a step too late)
To understand how Russia came to be viewed as such a threat that countries would turn in favour toward the country that had formerly been their main oppressor and occupier for centuries,you have to go back to the Ottoman Turks conquering Constantinople.
Russia at this point in her history,was a land locked small kingdom in the middle of the endlessly flat European plains,habitually harassed on her eastern frontier by steppe nomads,plagued by poor soil and precarious potential for trade outside of her borders.
Early in Russia's development,they found themselves hemmed in on all sides to the point where they could not develop the trade that they needed to stay a viable state. They had one seaport,White Sea,while not within the Arctic Circle,was still an inlet of the Arctic Ocean and could not be used for a good portion of the year. Russian soil quality was poor,requiring more acreage to feel its population than its European counterparts. That combination pushed Russia to expand her boundaries. In addition to the fact that when a young Ivan IV took the reins of power from his regency of nobles,he needed to prove his ability to hold together a fractious country - and how best to accomplish those goals?
A Successful Campaign of Conquering!
When Constantinople was overtaken by the Ottoman Turks in 1453,many Greek refugees fled northward to Moscow,an eastern orthodox stronghold. They brought with them experience in empire building - political,military and administrative knowledge that Russia did not have before this. At the time Ivan IV- the Terrible (aka Ivan the Dread)came into power in 1533,Russia was mired in a long period of chaotic struggles among its various internal political factions. Ivan used the knowledge Moscow gained from those immigrants from the Byzantine Empire to centralize administration of the state,strengthen and systemize the church's affairs,reform the country's legal code,reorganize the military forces from hereditary promotion to one of merit,and consolidate the tsar's hold on power. In addition,he expanded the country's borders - first he defeated the nomad tribes of KazanTurks to the east and gained access to the Urals,later he pushed Russia's control of Siberian territory northwest of Mongolia. He secured control over the Vogel River to the southern Caspian Sea so that trade route was safe from Tatar hostilities. He then attempted to force free access to the Baltic Sea from Latvia and Estonia.
And there he was stopped.