Because instead of a gradual progression and space infrastructure building (as was the original plan before Kennedy set the goal to Lunar landing before 1960s a

Because instead of a gradual progression and space infrastructure building (as was the original plan before Kennedy set the goal to Lunar landing before 1960s are over, its well documented in NASA history pages). As a result a space race with the Soviets developed, resulting in the USA winning & Soviets loosing - at a price. The Apollo hardware was a racing hardware, like a race car, build to win a race and little more. As a result, the whole program was horrendously expensive to run & it was politically unworkable to continue running it once a victory in the space race has been achieved. There was no shortage of people calling to continue not just with Moon but space exploration & industrialization in general (with a good example being Gerard O'Neill - https://en.wikipedia.org/wiki/Gerard_K._O%27Neill#Space_colonization https://en.wikipedia.org/wiki/Gerard_K._O%27Neill#Space_colo...). But they could never get the beancounters & shortsighted politicians to allocate the necessary costs to get things going. What I think changed is both the technology finally getting cheap enough that more entities can finally get involved without begging a government for a massive budget, because launcher reuse was demonstrated and even just because a bunch of very rich people who like space got involved & can do it themselves without depending on others.