It may have been, but I'd bet the Tony Conigliaro beaning in 1967 had as much to do with with the timing as anything.
Also agreed, but Chapman's death was cited as the biggest reason for the mandatory change, along with Mickey Cochrane's near-fatal and career-ending injury - Cochrane himself gave a statement saying that players should "absolutely have to wear protective headgear" - for the change. It didn't hold until much later, unfortunately; Ford Frick tried his best to make it mandatory, but it didn't stick.
But back to this subject: the new helmet could make Weird Al's "White and Nerdy" look like a fucking alpha jock, and I'd still prefer it over a player dying on the field or shortly after. Reputations can be lost or earned and kept; lives are absolutely irreplaceable.