There were concerns about some elements of what you're talking about with some WW2 generals. For example, MacArthur was at one point considered too popular for it to be politically feasible to fire him, after his insubordination during the Korean War.
In general, I suspect this change stems from a few things. One is that generals do not lead soldiers into combat as directly any more. Another is that soldiers no longer stand to personally profit from combat or war -- there is no taking of booty, raping and pillaging are at the very least heavily frowned upon, etc. And another thing is that combat actions are less frequent these days, so any given soldier has a shorter sequence of experiences and victories with a given commander.
But I'm not an expert historian. These are just some guesses.
In general, I suspect this change stems from a few things. One is that generals do not lead soldiers into combat as directly any more. Another is that soldiers no longer stand to personally profit from combat or war -- there is no taking of booty, raping and pillaging are at the very least heavily frowned upon, etc. And another thing is that combat actions are less frequent these days, so any given soldier has a shorter sequence of experiences and victories with a given commander.
But I'm not an expert historian. These are just some guesses.