How and why did the foreign policy of the USSR change after the Munich Agreement?

After the signing of the document, the threat loomed over the Soviet Union, as Germany, France, Italy and Great Britain signed a non-aggression pact against each other. It was a real conspiracy, because the meeting took place without the participation of the USSR and Czechoslovakia, although at this meeting the Germans were allowed to calmly take the lands of Czechoslovakia, as well as to conduct aggression towards V. Europe. Then the USSR, in order to protect itself, also began to negotiate with Germany and signed a non-aggression pact.