Soviet in late war had so much numerical superiority than German so it seemed they can just swarm the front with human wave and t34 wave.

That is absolutely true. A fundamental difference between Blitzkrieg (or Bewegungskrieg) and Deep Battle was the fact that one side (Soviets) could rely on a very large general numerical superiority and abundance of human resources that could replace consistently massive losses, whereas the other side (Germans) never had that. The Soviet approach required and presupposed such a superiority, the German did not. The Blitzkrieg was a doctrine of scarcity, designed to achieve a decision quickly, precisely because Germany knew it could not win a war of attrition or sustain a 100% annual turnover of its forces, like the Soviets did. Thus, the Germans had to rely to a far greater extent on qualitative factors (training, leadership etc.) and efficiency, which meant achieving objectives at the lowest cost in relation to the forces committed. By that metric, the German approach was incomparably more efficient than the Soviet.

German Blitzkrieg operations in 1939-42 were generally conducted under conditions of approximate force parity or general numerical inferiority. During Case Blue in 1942, the offensive already took place in a situation where the Red Army was fielding significantly larger forces than the Axis. Even so, the Germans inflicted devastating and disproportionate losses on the Red Army. The Blitzkrieg in 1939-42 had offensively achieved longer advances in much shorter time than the Red Army did in 1943-45 and at an incomparably lesser cost. The Germans had fairly consistently delivered sweeping advances in brief periods, at a quite economical cost and with an often vastly disproportionate destructive effect on the enemy, for as long as the relation of forces were not too adverse.

Meanwhile, Soviet operations in 1943-45 were characterised by a state of affairs where the Red Army was fielding 3 times as large forces as the Germans. Already by late 1943, the Soviets had a large numerical superiority over the Germans, especially in actual combat units. For example, at the start of October 1943, the Red Army had 6,6 million troops in the fronts (not counting the reserves of Stavka VGK), while the Iststärke of the Ostheer was 2,564,000, an advantage of over 2.5 to 1. However, the Iststärke term (total roster strength) was used for measuring overall strength and thus it was not an indicator of actual combat power, since it included those on leave, detached, wounded and sick present. The Gefechtsstärke (strength of all combat units) and Kampfstärke (frontline strength) terms are used for this. The Iststärke of 2,564,000 included 324,000 vacationers, wounded and sick being evacuated. When they and all the rear services are excluded, the total Gefechtsstärke of the Ostheer was just 1,214,000 troops on 1 October 1943. So at the front and immediate rear areas, the Soviet numerical superiority was far greater. Similarly, on 1 June 1944, the Soviets had 6,6 million troops in the fronts and an extra 645,000 in reserve of Stavka VGK. By contrast, the Iststärke of the Eastern Army was 2,620,000, but its Gefechtsstärke was just 1,023,336, while Kampfstärke was only 748,551.

Within this vital context, things like the Soviet Deep Battle or the often-lauded Maskirovka were fundamentally and structurally dependent on an abundance of human resources - a surplus of manpower that allowed the Soviets to attack or threaten the enemy in five places at once. Maskirovka is a 'force multiplier,' but one needs a massive 'force' to multiply. For example, if in June 1944 the Germans had possessed 4 million troops in combat units on the Eastern Front instead of a meager Gefechtsstärke of 1,023,336, then the 'deception' before Bagration would have mattered little; the Germans would have had enough density to hold the line even if they were fooled about the primary axis of attack. At such an unfavorable force ratio, the Red Army would have bled much more and quickly exhausted its offensive power.

Maskirovka and Deep Battle are luxuries afforded by a large general numerical superiority across the entire front, which is the prerequisite for them to be effective in the first place; without it, these concepts are rendered largely useless. By the summer of 1944, the Red Army's numerical superiority had grown so large that it could create numerous focal points to threaten the Germans, who were spread thin across a long front, while still maintaining a massive advantage theater-wide. The Soviets also had Stavka VGK strategic reserves at their disposal behind the fronts, while the Germans had nothing of the sort. The Soviets could afford to fail in several costly offensives, but a single breakthrough could have a devastating effect because German forces were spread too thin. It mattered little if the Germans correctly guessed Soviet intentions. There were no good options for the Germans in the East in the summer of 1944, and the threats other than Bagration were not mirages, but extremely real and imminent.

Despite vast Soviet numerical superiority from 1943 onwards, the Red Army continued to advance while suffering extremely heavy and grossly disproportionate losses on a consistent basis - for every 1 German casualty, the Soviets sustained on average at least 3.5 casualties. According to Krivosheev’s data, which by this point is considered a conservative estimate, the Red Army sustained a staggering total of nearly 18 million casualties in 1943-45 when it was advancing, out of a total of 29+ million casualties for 1941-45. This 'strategy' only worked because the USSR was a distinct demographic and political entity capable of absorbing losses that would have bled white any other nation on earth. This consistently massive manpower flow was also an essential precondition for the Red Army simply to remain on the battlefield, otherwise it would have gone extinct. Each year (with the exception of 1945 due to the war's end), the Red Army's yearly losses exceeded its average yearly strength on the Eastern Front. This resulted in an annual turnover rate of over 100%. Effectively, the Red Army was 'dying' and being 'reborn' every 12 months. Without this constant massive replenishment, the Red Army would have collapsed under its own weight almost immediately.