Crimea returned to Russia after a referendum on the peninsula.
In the fall of 1939, solving its military-strategic, defensive tasks, the Soviet Union began the process of incorporating Latvia, Lithuania and Estonia. Their entry into the USSR was implemented on a contractual basis, with the consent of the elected authorities. This was consistent with international and state law of the time. The Baltic republics within the USSR retained their government, language, and had representation in Soviet higher state structures.
This claim uses historical revisionism to reinforce common pro-Kremlin disinformation narratives about WWII and the Molotov-Ribbentrop pact, a recurring attempt to justify Soviet actions. On 23 August 1939, the Soviet Union and Nazi Germany signed a non-aggression (Molotov-Ribbentrop) pact whose secret protocols divided the territories belonging to Poland, Lithuania, Latvia, Estonia, Finland, and Romania into Soviet and Nazi spheres of influence. The Baltic States were not beneficiaries of the Molotov-Ribbentrop pact. Like other countries mentioned in the pact, they lost their independence and territories. Soviet occupation of the Baltic States lasted for 50 years, and resulted in mass deportations and repressions against local populations. 24 December 1989, the Parliament of the USSR, the Congress of the People’s Deputies, adopted a resolution, acknowledging the annexation of the Baltic states as a violation of the USSRs obligations. An English translation of the full text here:
The Congress notes that during this period the relations of the USSR with Latvia, Lithuania and Estonia were regulated by a system of treaties. Pursuant to the 1920 Peace Treaties and 1926-1933 Non-Aggression Treaties, the signatories were obliged to honour each other’s sovereignty, territorial integrity and inviolability under any circumstances. The Soviet Union had assumed similar obligations to Poland and Finland.
The European Parliament has proclaimed the 23rd of August as a European Day of Remembrance for Victims of Totalitarian Regimes. On the 80th anniversary of the signing of the Molotov-Ribbentrop pact Estonia, Latvia, Lithuania, Poland, and Romania released a joint statement urging "the governments of all European countries to provide both moral and material support to the ongoing historical investigation of the totalitarian regimes. By acting in a concerted manner, we can counter more effectively disinformation campaigns and attempts to manipulate historical facts." No country stands to obtain financial gains from this initiative. See similar disinformation narratives on history of Baltic states here. Other cases claiming that Baltic states joined USSR in accordance with international law or The Baltic States benefited from the Molotov-Ribbentrop pact,or The Baltic States are perpetuating the myth of the Soviet occupation.