It's always been this way, in every era. Someone smarter than me would probably say it's an outworking of Pareto distribution.
College football almost always has four or five dominant programs led by dominant coaches. Sometimes their success is built around a new offensive system, but not always. Success breeds success--and people with money love a winner.
Pick any decade of college football, compare which teams are in the preseason Top 10 over those 10 years, and you'll see it.
The only moments of "relative parity" among the top 15 teams usually come in one of those brief periods after a Bear Bryant or Woody Hayes or John McKay or Bud Wilkinson or Barry Switzer retires, leaving a vacuum where some perennially good program who puts it all together--with a little good fortune (like Tennessee in '98)--ascends to the top for a year.
That's why I hate the national championship playoff. Fan focus narrows to being that one team at the end, and everybody else is just another loser. The joy of college football used to be following how your own team is progressing year-to-year: your team's first appearance in the Top-20... first bowl game invite... going to a better bowl later in December... breaking into the Top-10... making a January bowl appearance... Fan excitement grew out of becoming a winner, not from just being the final winner.
Psychologists agree that our brains experience more pleasure, more reward, from the pursuit of our goals than from attaining our goals. The journey up is far better than trying to remain at the top. Bama fans get no real enjoyment from game days. All they can experience from a win is "Whew! We didn't lose."
That's why they're so obnoxious--the only enjoyment available to them is sticking it in everyone else's faces the other 6 days of the week. But if Bama doesn't win that final college game of the season, even if otherwise undefeated, their fans will have had a miserable year, and they won't get a chance to stop feeling like losers until the following January.