That Posnanski piece does a better job than any I have ever seen at explaining why the Cubs were terrible from 1946 thru the mid 1960's.
Phil Wrigley was an interesting and complicated man. He innovated baseball in quite a few ways (he was the man behind the All-American Girls Professional Baseball League and the ivy on the Wrigley Field walls). He was odd in many few ways; it was often said that he had no friends. Everyone agreed, though: Wrigley was deeply principled. He honestly did not want lights at Wrigley Field because he thought it would hurt the neighborhood. He believed in keeping Wrigley Field beautiful because he wanted baseball to feel like a picnic for families.
One of his deepest and most ingrained principles was trying to preserve the minor leagues -- so much so, he thought it insulting they even were called "MINOR leagues." Wrigley is probably the only owner in baseball history who actually WANTED there to be another major league -- no matter how much it might hurt his business -- because he thought it would provide more opportunity for fans and players. "Wrigley did not believe in farm systems," Bill Veeck writes in "Veeck As In Wreck." "It was his belief -- and he was right -- that baseball could only remain healthy if the minor league clubs were free to develop their own players and sell them to the highest bidder."
He may have been right in a moral sense, but his stance wasn't much good for building baseball teams. While other teams developed players by draining the minor leagues of talent and power, Wrigley's Cubs kept trying to do business the old-fashioned way. The only good young player the Cubs acquired from the end of the war until the late 1950s was Hall of Famer Ernie Banks, and that was old-business -- the Cubs bought Banks from the Kansas City Monarchs in the dying days of the Negro Leagues. They signed a few hard-throwing pitchers who did not pan out, but other than that they hardly even tried. The Cubs were terrible year after year.
All this happened in the immediate years after the Billy Goat's Curse -- and so the curse took on a life of its own. But there was no curse necessary in those early years of the Cubs streak. Without any real way to acquire or develop young talent, the Cubs for the first decade and a half after the war, didn't have stand chance.