And the work for achieving controlled nuclear fusion continues... A dream more than 80 years in the making.
That's a part of it, probably a very small part since laser pumped inertial confinement fusion is almost certainly a serious dead end.
What it is primarily intended for is to, as stated in the video, "support national security," as stated elsewhere in other nuclear lab videos, to provide nuclear weapon stockpile "stewardship" (making sure our existing nukes will still work without full scale testing), as
not stated anywhere but obvious to me according to the many pieces of publicly released data found elsewhere which I've previously linked to here, the verification by testing and measurement of the accuracy of predictions by computer codes which once perfected can then be used to design (without full scale testing) reliable highly optimized nuclear weapons and (speculating) ones with very interesting characteristics like extremely small size (hinted at by nuclear device designer Theodore B. Taylor decades ago), directed energy like a shaped charge (hinted at by nuclear device designer Theodore B. Taylor decades ago), devices with a very high percentage of clean fusion yield (the ideal), radiation spectrum optimized for EMP, etc.
Note that exactly the same kinds of computer codes which would be required to verify the continued functionality of existing designs would be just as useful in the creation of new designs.