That the rich became richer in the 1920s is a good thing...If there comes a day where the rich can't get richer, we're all going to be in one helluva fix.
That's not the point. The economy didn't reorganize itself after WWI for most people. The economy was bad for most people even as GDP rose. A small minority captured most of the gains of that decade. So using the 1920s as an analogy for cutting spending isn't a good one.
The mere existence of the GI bill didn't produce anything, in and of itself. The fact remains that post war federal spending plummeted and the economy reorganized itself into productive activities.
The government fixed interest rates for many years, and kept interest rates artificially low to pay off the massive amounts of debt accrued during the war. Not the Fed. The actual federal government passed laws. I doubt most free marketers would approve of such a policy today.