I had a look at RAND declassified reporting of the budget post WW2 and the Army was screwed hard. It was like policymakers thought the nuclear monopoly and the Air Force was so all important they didn’t even need an Army.
All the services suffered pretty badly. The Air Force and the nuclear deterrent were only neglected slightly less badly then the army and navy, and for such critical lynchpins they were massively under-resourced. Some of the issues with the nuclear deterrent were unavoidable, like the reactor problems that crimped bomb production from '45-'47, but the horror show that was late-'40s SAC is less excusable. I think it was largely instinct: every other major war in American history had seen the US forces mobilize up from miniscule to massive and powerful size in order fight it only to be absolutely disbanded back down too miniscule sizes with tiny budgets once the war was over and the fact that there was a Cold War going on took a few years to become obvious to the man-on-the-street, so there was too much political pressure to really avoid it. The bigger mystery to me is why it took as late as the Korean War for the catalyst to finally reverse the resource starvation of the armed services instead of, for example, the 1948 coup in Czechoslovakia, the Berlin Blockade & Airlift, the communist victory in the Chinese Civil War, or the Soviets acquiring an atomic bomb.