Reading the comments, it seems that there is a misunderstanding. I am asking about corporations with huge standing armies. I am asking why corporations are capable or eager of going to war in both settings, but it feels completely different when they do. There may or may not be a connection to actual nations and their actual militaries, or not. If this was a simple question, I would already know the answer.

The answer could have nothing to do with any nation's militaries and entirely be based on how the Megacorps make money. It could be the time period of each being different, it could be the condition of the land or how broken up the nations are. The difference could be that one setting is more messed up then the other, or one setting has had less nations going to war with each other, so corporations are less afraid of serious conflicts. The issue is that being an expert in one, won't answer this question. Asking about the nations militaries won't answer this question. This question might.

Neither setting has the militaries completely taken apart or grown, they are just smaller, leaner machines. I'm asking why Megacorps in Cyberpunk 2020, have standing armies that are the same size as normal armies now, and have the same firepower, and use that firepower in actual wars.