The purpose of NIF, and it’s not hidden, is to maintain the existing US nuclear stockpile since we can no longer rely on using underground nuclear weapon testing to ensure they still work. There’s a very big supercomputing capability funded under the same effort. Instead of testing the weapons by exploding them underground, we use computer modeling with the modeling validated (ie backed up) by experiment (at NIF) to make sure the stockpile works and can maintain its strategic deterrent. The euphemistic name for this is “stockpile stewardship.”
The B53 bomb was built in 1961 and it released 38 PJ or 10 BILLION times more energy than this experiment. Data gathered about plasma and fusion at NIF temperatures and pressures is not helpful for the insanely different environment of a nuclear bomb.
> What do you think the US nuclear weapons research lab will use their research for?
Why do you think that fusion is not enough? Complete strategic energy independence for the US, and dominance in the electricity sector? That's so, SO much more valuable than better nuclear weapons.
You're right that increasing the yield was a bad example from my side, but the purpose is to improve the weapons, nothing else.