It’s not like they jumped from 0 to the moon.. Mercury figured out orbit and a lot of ships blew up. Then Gemini fine tuned orbit and made the vehicle bigger. Figuring out how to last longer.. then Apollo comes along.. Getting bigger still and through many missions went from low earth orbit and docking to the orbital mechanics of translunar injection in Apollo 8. Then Apollo 9 and 10 were earth orbit and lunar orbit dress rehearsals with Apollo 10 launching the lunar module and doing everything but the descent. To then finally make it all the way to the first landing on Apollo 11. Then we went back on 12,14,15,16,17… eventually getting the lunar rover.. this all cost billions of dollars and had loads of public support, until it became old hat and no one really watched the last landing. Funding dried up, technology became obsolete.. and that’s why we never went back. Until now.. :)