Look at some of the directors of those old western series, there are some heavy hitters among them.
Like so much back then, people had lived a lot of life and they brought that to their art, their writing, their newspaper reporting, their acting, there was more depth, breadth, and knowledge throughout our entire culture.
Right you are.
WW I was still in living memory as was the depression and WW II. As you say, a lot of living in those people at the time. Writing about life on the frontier was a natural for them.
Plus, the frontier had closed only 60 years before 1950, so frontier life was still in living memory as well.