Suvorov grew up hearing and reading about this, but also coming to learn and understand that as a rule Soviet propaganda thoroughly hid any mistakes, accidents, and catastrophes in the Soviet Union; or tried to downplay what happened as not that bad; or tried to blame it on the nefarious enemies, while avoiding crediting the enemy as much as possible: the enemy cheated, that's the only way they could do that.
The official Soviet propaganda about Barbarossa did talk about the Nazis as cheaters who attacked by surprise without declaring war and without even giving formal grievances for attack; but also talked about how the Nazis were so much technically better than Soviets at that time: much better equipment, much better training for their troops, much more skilled in their leaders.
Soviet propaganda didn't want to talk about an earthquake leveling a city of one hundred thousand people -- but wanted to talk about bad tanks authorized by Stalin? Soviet propaganda wanted to hide any number of bad harvests, or blame them somehow on being surrounded by capitalist nations -- but wanted to talk about radical mismanagement of the Soviet military?
In 1942, the Red army suffered monstrous defeats in the Crimea, also near Kharkov, also at Leningrad, also at Rzhev. One of Suvorov's own most virulent critics among professional historians of the Soviet war, David Glantz, discovered traces of insanely huge tank battles lost by the Soviets in the first half of the war -- lost to history, too, due to Soviets intentionally destroying those records (and to Nazis destroying their own records generally when they later realized they were going to lose). How did Glantz find out about these larger precursors to the later and far more famous armored battles of Kharkov and Kursk? By using the same methods of Suvorov, of course: indirectly tracing the battles by checking production numbers and the memoirs of Soviet and Nazi commanders, and other such things. (Thus, incidentally, confirming many of the details he has denied when Suvorov presents them!)
The crucial point of comparison here, is that Soviet propaganda didn't want to talk about those losses in their accounts of the war soon afterward, and in their textbooks for a long time going forward. It was not acceptable to talk about the defeats of 1942 -- so why was it acceptable to talk about the defeats of 1941, soon afterward and in their textbooks going forward?
Moreover, in July, August, September, and October of 1941, the Red Army suffered crushing defeats near Viazma, Uman, Kiev, and most importantly Smolensk -- most importantly because that crushing defeat nevertheless derailed the Nazi blitzkrieg and could be easily argued as the reason the Soviet Union survived until 1942! Soviet history books did not, and into the early 21st century still did not, want to mention those defeats. It was not acceptable in propaganda control to talk about the specific defeats of 1941, soon afterward and in their textbooks going forward -- and yet, soon afterward, and in their textbooks going forward, Soviet propaganda, even controlled and authored by Stalin, wanted to trumpet its own criticism of how stupid and unfit for a fight the Soviet military was, especially under Stalin, which led to those specific defeats?!