One take on this - those rare few who did the "long and hard way" were not as lazy / stupid / warlike / etc. as us mere humans. And maybe they took 750k years, or some other really long https://tvtropes.org/pmwiki/pmwiki.php/Main/HardWorkMontage stuff.

But a related take - if you just move the "seems inexplicable" stuff further away in space and time, then most people magically see it as being less inexplicable.