You can't really understand Hitler's attack on the USSR without considering Lebensraum - the policy of developing an "agrarian empire" in the east, on largely Ukrainian soil, to make Germany self-sufficient and strengthen it against attempts by other powers to contain and undermine it. There was no need for the West to "push" Hitler to look to the East. As we can safely assume that the Soviets were not going to hand over the territory to Hitler, we must accept there was going to be a war between the two.
The idea of Lebensraum was outlined in Mein Kampf, although Hitler downplayed it once he got into power. A Lebensraum Plan" was never formally created (although there is the Hossbach Memorandum), but as Hitler had total control he only needed to have the intention, however vague, and issue firm orders at appropriate times. From the time of his ascension to power Hitler followed a distinct path towards his goal - consolidate his power in Germany, set the country off onto an economic growth path cum war-footing, build up the will of the people, reverse the clauses of the Versailles Treaty, recover many lost German lands, build a continental anti-communist coalition, consolidate influence on Soviet bordering states and then eventual attack of the Soviet Union.
The question was timing, gathering the required resources and the strategy of avoiding conflict with the west and avoiding the potential for a two-front war. Hitler believed the West was weak and would not commit to any firm action against him. However, he understood that it was possible and that he would have to manage that possibility. The economic times left much of Europe poor and looking for a way out, providing favourable grounds for Hitler to offer them (and himself) economic benefits for eventual political acceptance of his views against the Soviets. Hitler also understood that the Soviets could only be beaten when they were internally weak - and this placed a time constraint for when action could be taken; the longer an attack was delayed the greater the chance the Soviets had progressed down the path of rebuilding and renewal and withstanding an attack.
There was no time to lose for Hitler as once the Soviets moved past the purges of the 1930's they would quickly regain strength that would make an attack by Germany not feasible. The path to get Germany to the point where it could mount an attack was demanding - inevitably Hitler was forcing plans ahead of what his advisers believed was sustainable. But this was the impact of Hitler's understanding of timing. The purges were coming to an end and the Soviets would soon move to a rebuilding phase.
Once the Munich agreement was signed Hitler began moving to the eastern consolidation phase of his plan, and immediately he met resistance - firstly from the Poles who refused to consider his "rather reasonable requests", and then after taking Czechoslovakia, the British guarantee to Poland. The odds for a two fronted war had increased. An effective resistance to Hitler required a strong force in the East, and that could only be the Soviet Union. Given the British and French unpreparedness for war Stalin feared that the Soviets will be left doing most of the fighting for the West's benefit, perhaps even at the expense of the Soviet Union itself. Furthermore, nothing was being offered for his efforts. But there was a threat from Germany. The idea of treating with Hitler to buy time arose and the Molotov Ribbentrop Pact was born. The Soviets found the German much easier to deal with, making decisions in a timely manner and offer rewards for the effort. Germany could now attack Poland with the Soviet Union acquiescing, and if the West were to attack, deal with that without any worry from the East. When any conflict in the west was settled he could focus on the East again.