The Kelly Bills, Moon Oilers, and 80's Steelers were championship teams? That's news to me. Let's see it took the Astros 5 seasons to make the playoffs and 7 to finally win a World Series. Let's take a look at the teams you listed:
The 80's 49ers took 3 years to win a Super Bowl with Walsh, going 2-14 and 6-10, you know showing improvement as they built.
The 80's Giants took 4 years to win a Super Bowl with Parcells going 3-12-1 his first year, but became a playoff contender after that.
I'm going to guess you meant the 70's Steelers, I guess comparable to the Stros. It took Noll 4 years to turn them into a playoff contender, going 1-13, 5-9, and 6-8 in his first three seasons, still showing improvement. In year 6 they got over the hump, after a legendary draft where they picked 4 HOFers.
Also these teams were all the pre-salary cap era, so you could just keep all those good players you picked, you didn't have to worry about free agency. So uh, you got any examples in the salary cap era?