The NFL did an excellent job on this site as covers the history of American professional football.
No doubt this quiet launch is part of the NFL's legal strategy though there is ample evidence, including especially its allowance of the wedge formation on kickoffs until 2009 well after "the flying wedge" was banned in 1894 in American Football (short film clip shown), that the NFL let the guys play injury prone with the wedge formation allowed on kickoffs too long.
Now on this crap about eliminating kickoffs, that's just plain bull and will ruin the game.
All the NFL has to do is eliminate also the high hits altogether except on a ball carrier who is not standing upright. It's by nature a violent game otherwise when there is deliberate physical contact and ultimately legal clobbering. No one is forced to play any such sport.
Check out for example the changes in the ball:http://evolution.nfl.com/#/nfl-football-1958
Our ball had the stripes like yours in the 1960s too. I have one replica of the prior ball and two actual "Dukes" now.
Otherwise overall the game of American football does not look like it resembled anything like the modern game until into the 1950s.
For example, as I had no idea, until 1956 the rules on tackling matched for the most part that of rugby union until the rule on "down by contact" was introduced. There is a film clip on it. That means so long as movement was not stopped even after a runner was chopped or shoved down, a runner could get back up and run just like in rugby (provided he releases the ball in rugby first before picking it up).