A lot of this feels like alternate history, but the historic theory that seems to be underlying this is that the Western Allies landed at Normandy specifically to keep the Soviets out of Western Europe. In other words, that it was less about fighting Nazi Germany than making a power play for a future Cold War Europe.

The biggest problem that I can see with this theory is that the Soviets repeatedly and insistently demanded that the UK and US invade Western Europe. Indeed, if anything it was a major bone of contention between the Soviets, British and Americans that it took so long for this to happen.

Stalin and the rest of the Soviet government knew that for most of the war the Soviets were by doing the brunt of the land fighting (and making casualties far, far greater than what the Western Allies suffered), and as a result made repeated calls to the British and American governments to open a "Second Front" in France. These calls came as early as spring 1942, when Vyacheslav Molotov made his rounds in London and Washington, and were given urgency considering that the Wehrmacht had just launched their renewed offensives that would ultimately lead them to Stalingrad. Indeed, there was a joke in London circles that Molotov only spoke four words of English: "yes", "no", and "second front". Churchill evaded a commitment to Molotov, citing the North African Desert campaign and air war over Germany as second front substitutes and noting that there was a lack of amphibious equipment to mount a successful cross-channel invasion.

Molotov then traveled to America, and received a different reception from FDR, who on a number of occasions promised both in private and in a public joint communique to open a second front in France in 1942 (I highlight because this is a little astounding from our perspective).

News of this alarmed Churchill (who knew that a cross-Channel attack that year would mostly involve British and Commonwealth troops - the US military was nowhere near as mobilized) who hastened to the US, and met with FDR at Hyde Park. He managed to talk FDR down from a cross-Channel invasion in favor of the North African campaign that commenced that fall. The US military senior officers actually opposed this in favor of the cross-Channel invasion (the plans were known as Operation Sledgehammer), but Churchill prevailed upon FDR, and the Dieppe raid fiasco in August seemed further evidence that such an invasion required more logistical planning than was ready and available that year. The Soviets were irritated at these plans - it actually meant a 40 percent reduction in Lend Lease shipments to them as the UK and US marshalled supplies for a campaign that the Soviets considered a sideshow, and Churchill next flew to Moscow to meet with Stalin, and mollify him and the Soviet leadership by discussing a stepped-up bombing campaign over Germany (the minutes show that Churchill literally offered a campaign to break German civilian morale and to "shatter almost every dwelling in almost every German city" to cheer Stalin's morose mood over the news about a delayed Second Front). The Combined Bomber Offensive that came out of the Churchill-FDR conference at Casablanca in January 1943 ultimately owes its existence to this.

The Casablanca Conference also had another major impact regarding the Second Front - the US and UK agreed that the termination of the North African campaign would be followed by an invasion of Italy. The US military again was opposed to this, wanting a cross-Channel invasion in 1943, but Roosevelt ultimately agreed to the further delay in return for a promise from Churchill to contribute more to the Pacific War.

Stalin again was extremely upset by the news, writing directly to FDR that an invasion of Sicily "can by no means replace a second front in France", but again there was little he could do otherwise beyond protesting.

To skip ahead a bit, these demands from the Soviets never went away, and finally bore fruit at the Teheran Conference between FDR, Churchill and Stalin in November 1942. Roosevelt and the Americans, as can be seen, had long been much more willing to undertake a cross-channel invasion, with Stalin and Roosevelt being more on the same page, and Churchill being the holdout. Long negotiations finally produced a commitment from all parties for Operation Overlord, which was to commence in May 1944 (and be supported by coordinating attacks on the Eastern Front and in Italy).

A final point is that even in June 1944, while the defeat of Germany was on the horizon, it was still far from a done deal. Even in June 1944 large chunks of Belorussia and the Baltics were under German control, and this was only changed with Operation Bagration, one of the largest operations (and biggest German defeats) on the Eastern Front - and this indeed was the promised supporting operation for Overlord.

So in summary - the Soviets repeatedly called for a cross-channel invasion of Western Europe by the UK and US, and did so for almost the entire length of the war. The US military was very open to the idea from the beginning, but Churchill and the British government and military were extremely skeptical of such plans, and delayed them as long as they could until political pressures meant that all sides agreed to this invasion in May/June 1944.