Why Did Science Die in Specifically the 70s?

Duh, of course science died in the early 70s. That's when the Old Left was ousted by the New Left, in other words when pre-war non-communist trained administrators were replaced by properly post-war communist administrators. 

Science was mortally wounded by nationalization in 1945, but nevertheless for a time universities contained many pre-war scientists and thus there was a bunch of inertia. The 70s is rather awkward for timing, though. 

Someone who got their doctorate in 1945 can easily be expected to stay in the system until the mid-80s, so it's not age-related selection. Also, due to old_dogs/new_tricks, these prewar doctorates should have trained more prewar doctorates, with only minor contamination driven primarily by (corrupt) innovation. Science should have died relatively slowly.

On the other hand, most discovery work is done in your 20s and 30s, meaning science should have died by the mid-60s at the latest.

Instead, it was an old_dogs kind of situation, except a bunch of political entrepreneurs recognized the new regimes for the communist-safe space it was, and pressure rapidly built up until they simply launched the revolution. Society evolves faster when it's smart and rich. They recognize the Nash equilibrium sooner.
The revolution worked, because they weren't wrong about making the world safe for communism. By the early 70s they consolidated their position, forced the scientific community to fall in line, and thoroughly cremated the corpse of free discovery.

Prewar scientists were already leftist, and thus politicized, but they had priorities other than politics. Like a well-rounded human being or something silly like that. American is totalitarian, so we can't have that, now can we? 

P.S. Nobody should getting married and the welfare rolls should be at least three times bigger than they in fact are, except inertia. The lower classes are poor and dumb and recognize the Nash equilibrium super slowly. Being a net taxpayer is a sucker's game in modern America, but luckily for USG America has always been stuffed to the brim with suckers.

On the downside, most forms of net tax consumer are also suckers' games.