Technology certainly has a place but I would not consider it THE reason. Heck TO was welcoming Florida State and Bobby Bowden to Lincoln to showcase his organization. FSU copied everything and went onto a glorious run of success ... done well before the internet age.
IMO to address the question ... THE reason for the differences is television ... more specifically the money generated from television. Back in the days of Devaney there were only 3 dozen teams actively playing high level collegiate football. It simply was not worth the amount of investment required to field a team that made money. The money they made back then paled in comparison to today's environment. Back then no one heard to Boise State or UCF or Utah or K-State or Troy or Northern Illinois ... so on and so forth. Nowadays the list of colleges with teams capable of competing for the top 25 is huge.
Biggest difference is ... money (more specifically money generated by television revenues).
Yeah isn't what you are describing parity? GFOA doesn't think it exists and for the top 8-10 teams it doesn't. There are a lot more good teams than their used to be. In the 70's and 80's Nebraska had 6 gimmies most years in the Big 8. ISU, OSU, KSU, KU, CU, and MU were not very good most of the time, they might take turns being decent for a while, but nothing sustained. Everyone of those teams now is decent expect KU. You better show up to play or you will lose to those teams. That is parity. Same goes for the B1G. RU and Illinois are the only true dogs in the bunch.